               IN THE SUPREME COURT OF IOWA
                                  No. 13–1009

                               Filed April 3, 2015

                          Amended June 11, 2015


ROBERTS DAIRY and CRAWFORD & COMPANY,

      Appellees,

vs.

GRADY BILLICK,

      Appellant.


      Appeal   from      the   Iowa    District   Court   for   Polk   County,

Christopher L. McDonald, Judge.



      A workers’ compensation claimant appeals the district court’s

ruling on judicial review of a decision of the Iowa Workers’ Compensation

Commissioner. REVERSED AND REMANDED WITH INSTRUCTIONS.



      Thomas J. Currie of Currie & Liabo Law Firm, P.L.C., Cedar
Rapids, for appellant.



      Stephen W. Spencer and Joseph M. Barron of Peddicord, Wharton,

Spencer, Hook, Barron & Wegman, L.L.P., West Des Moines, for

appellees.
                                      2

HECHT, Justice.

        An employee sought workers’ compensation benefits for a series of

work-related injuries.    His current employer contends its liability for

industrial disability benefits must be apportioned because the employee

previously suffered disability as a consequence of two separate injuries

sustained while working for other employers. The workers’ compensation

commissioner concluded apportionment of industrial disability is not

mandated by law under the circumstances of this case.            On judicial

review, the district court concluded the commissioner’s decision was

based    on   a   misinterpretation   of   amendments   to   our    workers’

compensation statutes passed in 2004. The district court reversed the

commissioner’s decision and remanded the case to the agency for further

findings relevant to the apportionment issue.     Finding no error in the

commissioner’s interpretation of the relevant statutes, we reverse the

district court’s ruling and remand with instructions.

        I. Background Facts and Proceedings.

        The following facts are supported by substantial evidence in the

agency record for this case. In 1985, Grady Billick sustained a back

injury while working for Squealer Feed Company in Iowa.            He later

settled his workers’ compensation claim against that company for

payment based on an eighty-five percent industrial disability.

        In 1993, Billick was again injured while working for Milky Way

Transport. On that occasion, he lost control of a tanker truck he was

driving in inclement weather. The truck crashed and Billick sustained

injuries to his head, neck, left shoulder, ribs, back, and left arm. His

workers’ compensation claim for these injuries was settled under

Missouri law for an amount representing 18.5% permanent partial

disability of the body as a whole.
                                     3

      Billick began working for Roberts Dairy (Roberts) in 2001.       The

employment required Billick to drive a semi-truck and deliver milk

products from Iowa City to various retail stores across the state.     The

trucks were generally loaded by others, but Billick was required to

unload them himself upon arrival at points of delivery.

      Billick suffered four work-related injuries while working for

Roberts. In March 2004, a dolly carrying milk crates struck Billick’s left

ankle and trapped it against a dock plate. Despite treatment, including

an arthroscopic surgery, Billick was left with permanent impairment and

experiences residual pain and swelling in his left lower extremity.

      In June 2004, shelving in a Wal-Mart store collapsed while Billick

was making a delivery there for Roberts. The shelving struck Billick’s

head, neck, and left shoulder, and knocked him to the ground. He

received treatment for left shoulder and neck pain which led to shoulder

surgery. Billick was assigned a partial permanent physical impairment

rating for this injury.

      In 2006, rusty bolts on a trailer strap came loose when Billick used

the strap while pulling a truck door shut. He lost his balance, fell out of

the truck, and injured his left arm and elbow. An MRI study performed

on the day of this injury revealed a thoracic compression fracture.

Billick lost no work as a consequence of this injury.

      In 2007, a misaligned loading dock at a store in Altoona caused

several milk crates to fall off a dolly.   The crates struck Billick in the

chest and shoulder. While driving back to Iowa City after sustaining this

injury in Altoona, another vehicle’s erratic movement caused Billick to

steer his truck off the road. The emotional trauma resulting from the

near-crash combined with and superimposed on the chest injury he
                                          4

suffered earlier that day made Billick quite distraught and produced a

physical–mental injury.

      Billick filed four workers’ compensation petitions against Roberts.

The claims were consolidated for hearing.               The commissioner’s appeal

decision awarded Billick healing period benefits for various periods of

temporary total disability, permanent partial disability benefits for a loss

of twelve percent of his left lower extremity, and permanent partial

disability benefits for the loss of thirty-five percent of his earning capacity

for the unscheduled components of injury.

      The commissioner rejected Roberts’s contention that its liability for

Billick’s industrial disability should be apportioned because Billick was

previously compensated for his losses of earning capacity arising from

the 1985 and 1993 injuries through settlements in Iowa with Squealer

Feed and with Milky Way in Missouri.               Both parties sought judicial

review of the commissioner’s appeal decision.

      Although the parties’ petitions for judicial review challenged—and

the district court’s decision addressed—numerous aspects of the agency

decision,   the   only   issue   before       us   on    appeal   is   whether   the

commissioner’s ruling on the apportionment issue based upon his

interpretation of the legislature’s 2004 amendments to Iowa Code

chapter 85 was correct. The district court concluded the commissioner

misapprehended the relevant statutes and therefore reversed and

remanded the case to the agency for further findings of fact relevant to

the apportionment issue.

      Billick appeals from the district court’s decision on judicial review.

We retained the appeal to interpret the 2004 amendments and decide

whether the commissioner erred in concluding Roberts’s liability for
                                         5

permanent partial disability benefits cannot be apportioned under the

circumstances of this case.

      II. Scope of Review.

      “Iowa Code chapter 17A governs judicial review of the decisions of

the workers’ compensation commissioner.” Mycogen Seeds v. Sands, 686

N.W.2d 457, 463 (Iowa 2004).             Under chapter 17A, we are free to

substitute our own interpretation of statutes “whose interpretation[s]

ha[ve] not clearly been vested” in the agency. Iowa Code § 17A.19(10)(c)

(2007); see also Mycogen Seeds, 686 N.W.2d at 464.                 To determine

whether the legislature clearly vested an agency with authority to

interpret particular statutes, we consider “the phrases or statutory

provisions to be interpreted, their context, the purpose of the statute,

and other practical considerations . . . as well as the functions of and

duties imposed on the agency.” Renda v. Iowa Civil Rights Comm’n, 784

N.W.2d 8, 11–12 (Iowa 2010).

      The legislature has not expressly granted the commissioner the

power to interpret Iowa Code sections 85.34(2)(u) and (7)(a)—the statutes

at issue in this case. It has “granted to the commissioner the authority

to ‘[a]dopt and enforce rules necessary to implement’ chapters 85, 85A,

85B, 86 and 87.”       Waldinger Corp. v. Mettler, 817 N.W.2d 1, 5 (Iowa

2012) (alteration in original) (quoting Iowa Code § 86.8(1)(a) (2011)).

However, standing alone this does “not constitute a clear vesting of

interpretive authority.”     Id. at 7.   Sections 85.34(2)(u) and (7)(a) leave

undefined several terms and phrases bearing on this case, such as

“earning   capacity”   and     “preexisting   disability.”   See    Iowa   Code

§§ 85.34(2)(u), (7)(a) (2007).     The presence of undefined terms and

phrases in these sections suggests the legislature did not clearly vest the
                                        6

agency with authority to interpret those terms and phrases.                   See

Waldinger Corp., 817 N.W.2d at 7.

      We conclude the legislature did not clearly vest the commissioner

with authority to interpret the subsections of Iowa Code section 85.34 at

issue in this case.       “Accordingly, our review of the commissioner’s

interpretation . . . is for correction of errors at law.” Id.

      III. The Parties’ Positions.

      Billick   asserts    the   district   court   erred    in   reversing   the

commissioner’s determination that Roberts is not, as a matter of law,

entitled to apportionment under the circumstances presented here. He

contends the commissioner correctly concluded the 2004 amendments to

Iowa Code section 85.34 did not modify the fresh-start rule for an

industrial disability claim made by a claimant who was previously

compensated for a loss of earning capacity suffered as a consequence of

an unscheduled injury that occurred while working in the course and

scope of employment for a different employer.               Billick contends an

interpretation of section 85.34 allowing Roberts a credit for any disability

compensated by previous employers would inflict upon him an

unwarranted reduction in benefits not intended by the legislature when it

amended the Iowa Workers’ Compensation Act in 2004. Further, Billick

suggests the district court’s interpretation of the 2004 amendments

circumvents the fundamental purpose and intent of Iowa Code chapter

85—which is to benefit injured workers and their dependents.                  See

McSpadden v. Big Ben Coal Co., 288 N.W.2d 181, 188 (Iowa 1980).

      Conversely, Roberts asserts the commissioner’s interpretation of

the 2004 amendments contravenes the legislature’s clearly stated

purpose underlying the enactments and would allow Billick a double

recovery for his consecutive losses of earning capacity. See 2004 Iowa
                                      7

Acts 1st Extraordinary Sess. ch. 1001, § 20.           Roberts contends the

legislature’s 2004 amendments were intended to abrogate the concept of

full responsibility by specifically indicating employers will not be held

responsible for disability sustained through a prior work injury. Roberts

further contends the commissioner erred in denying it credit for 425

weeks of permanent partial disability benefits paid by Billick’s prior

employers.    Accordingly, Roberts requests that we affirm the district

court’s ruling remanding this case to the commissioner for new findings

on the extent of Billick’s loss of earning capacity.

      IV. Analysis.

      A. Law Antedating the 2004 Amendments. The resolution of the

issue presented for our decision turns on the legal effect of the

legislature’s 2004 amendments to Iowa Code section 85.34. Because the

legislature expressly intended the amendments to “modif[y] the fresh

start and full responsibility rules of law announced by the Iowa

[S]upreme [C]ourt in a series of judicial precedents,” 2004 Iowa Acts 1st

Extraordinary Sess. ch. 1001, § 20, our analysis begins with an overview

of those rules as they had been previously applied.

      1. The fresh-start rule.      The fresh-start rule is a theoretical

construct presuming that when an employee who has sustained a work-

related injury resulting in permanent partial industrial disability begins

employment with a new employer, the employee enjoys a renewed

earning capacity. A preeminent workers’ compensation treatise explains

the reasoning behind this rule:

            The capacities of a human being cannot be arbitrarily
      and finally divided and written off by percentages. The fact
      that a person has once received compensation . . . for 50
      percent of total disability does not mean that ever after he or
      she is in the eyes of compensation law but half a person,
      never again entitled to receive a compensation award going
                                        8
         beyond the other 50 percent of total. After having received
         the prior payments, he or she may, in future years, be able
         to resume gainful employment. . . . If so, there is no reason
         why a disability which would bring anyone else total
         permanent disability benefits should yield that person only
         half as much.

8 Arthur Larson & Lex K. Larson, Larson’s Workers’ Compensation Law §

92.02[7][c], at 92-10 (rev. ed. 2014); see also Ziegler v. U.S. Gypsum Co.,

252 Iowa 613, 620, 106 N.W.2d 591, 595 (1960) (“It is . . . well settled

that when an employee is hired, the employer takes him subject to any

active     or   dormant    health   impairments    incurred   prior   to   this

employment.”).      Under the fresh-start rule, if the employee sustains a

new work-related injury after commencing work for a new employer, any

resulting loss of earning capacity is measured as a diminution of the

new, complete earning capacity that existed at the time the employment

with the new employer commenced.

         2. The full-responsibility rule.   The full-responsibility rule is a

functional corollary of the fresh-start rule.     Floyd v. Quaker Oats, 646

N.W.2d 105, 110 (Iowa 2002) (noting our decision in Celotex Corp. v.

Auten, 541 N.W.2d 252 (Iowa 1995), “was a recognition . . . that

application of the full-responsibility rule in body-as-a-whole disability

situations is based on the premise of a fresh start with respect to

industrial disability” (emphasis added)). “When there are two successive

work-related [unscheduled] injuries, the employer liable for the second

injury ‘is generally held liable for the entire disability resulting from the

combination of the prior disability and the present injury.’ ”         Second

Injury Fund v. Nelson, 544 N.W.2d 258, 265 (Iowa 1995) (quoting Celotex

Corp., 541 N.W.2d at 254).

         3. Venegas v. IBP.    The practical consequence of the employee’s

fresh start and the successor employer’s full responsibility in the context
                                          9

of successive unscheduled injuries before the 2004 amendments was

illustrated by our decision in Venegas v. IBP, Inc., 638 N.W.2d 699 (Iowa

2002). In Venegas, the claimant sustained a back injury that caused a

thirty-five percent permanent partial industrial disability while working

for an employer in California. Id. at 700. Years later, while working for a

different employer in Iowa, the claimant sustained another back injury

resulting in a fifty-five percent industrial disability. See id. at 700–01.

The commissioner apportioned the award of industrial disability benefits

for the latter injury and ordered the second employer to pay benefits

representing an award of twenty percent disability.              Id. 1   However, on

judicial   review,   the    district   court   concluded      apportionment       was

unwarranted “and that IBP was responsible for the total amount of

[Venegas’s] industrial disability.”      Id. at 701.     We agreed and held the

full-responsibility rule should apply due to the fresh start Venegas

gained when he began work in Iowa for a new employer. See id. at 701–

02.

       B. The 2004 Amendments to Section 85.34.                          In a special

session of the general assembly held in 2004, two amendments to section

85.34 were adopted.        The first of these was an amendment to section
85.34(2)(u), which provided as follows:


       1Prior  to the 2004 amendments, we noted the full-responsibility rule could also
apply where a claimant sustained successive injuries resulting in permanent disability
while working for a single employer. Excel Corp. v. Smithart, 654 N.W.2d 891, 898 (Iowa
2002). Notwithstanding, we concluded apportionment was necessary in Smithart
because the claimant was receiving workers’ compensation weekly benefits for a prior
work-related injury when the new injury occurred. Id. at 899. Under Iowa Code section
85.36(9)(c) (2001), apportionment was mandated because the benefits owed to Smithart
for the two injuries overlapped. See Smithart, 654 N.W.2d at 899–900. The legislature
repealed section 85.36(9)(c) in 2004. 2004 Iowa Acts 1st Extraordinary Sess. ch. 1001,
§ 12.
                                        10
            u. In all cases of permanent partial disability other
      than those hereinabove described or referred to in
      paragraphs “a” through “t” hereof, the compensation shall be
      paid during the number of weeks in relation to five hundred
      weeks as the reduction in the employee’s earning capacity
      caused by the disability bears in relation to the body of the
      injured earning capacity that the employee as a whole
      possessed when the injury occurred.

2004 Iowa Acts 1st Extraordinary Sess. ch. 1001, § 10. 2             The second

significant aspect of the amendments was the addition of a new section

numbered 85.34(7). It provides, in relevant part, as follows:

      7. SUCCESSIVE DISABILITIES.

            a. An employer is fully liable for compensating all of
      an employee’s disability that arises out of and in the course
      of the employee’s employment with the employer. An
      employer is not liable for compensating an employee’s
      preexisting disability that arose out of and in the course of
      employment with a different employer or from causes
      unrelated to employment.

            b. If an injured employee has a preexisting disability
      that was caused by a prior injury arising out of and in the
      course of employment with the same employer, and the
      preexisting disability was compensable under the same
      paragraph of section 85.34, subsection 2, as the employee’s
      present injury, the employer is liable for the combined
      disability that is caused by the injuries, measured in relation
      to the employee’s condition immediately prior to the first
      injury. In this instance, the employer’s liability for the
      combined disability shall be considered to be already
      partially satisfied to the extent of the percentage of disability
      for which the employee was previously compensated by the
      employer.

            If, however, an employer is liable to an employee for a
      combined disability that is payable under section 85.34,
      subsection 2, paragraph “u”, and the employee has a
      preexisting disability that causes the employee’s earnings to
      be less at the time of the present injury than if the prior
      injury had not occurred, the employer’s liability for the
      combined disability shall be considered to be already
      partially satisfied to the extent of the percentage of disability

        2In our reproduction of this amendment, underlining indicates additions and

strikethrough indicates deletions.
                                   11
      for which the employee was previously compensated by the
      employer minus the percentage that the employee’s earnings
      are less at the time of the present injury than if the prior
      injury had not occurred.

            c. A successor employer shall be considered to be the
      same employer if the employee became part of the successor
      employer’s workforce through a merger, purchase, or other
      transaction that assumes the employee into the successor
      employer’s workforce without substantially changing the
      nature of the employee’s employment.

Id. § 11.

      The legislation included a statement of the general assembly’s

legislative intent in adopting these amendments to section 85.34.      In

relevant part, the statement explained the statutory changes would

“prevent all double recoveries and all double reductions in workers’

compensation benefits for permanent partial disability.” Id. § 20. The

statement of legislative intent further clarified that the amendments to

section 85.34 “modifie[d] the fresh start and full responsibility rules of

law announced by the Iowa [S]upreme [C]ourt in a series of judicial

precedents.”     Id.   Yet, the statement notably revealed the general

assembly did not intend to eliminate the fresh-start rule altogether. It

instead recognized the continuing vitality of the fresh-start rule as

modified by the amendments:

      The competitive labor market determines the value of a
      person’s earning capacity through a strong correlation with
      the level of earnings a person can achieve in the competitive
      labor market. The market reevaluates a person as a working
      unit each time the person competes in the competitive labor
      market, causing a fresh start with each change of
      employment.

Id. The statement emphasized in clear terms that the general assembly

intended no change of existing law “that is not expressly provided” in the

enactment. Id.
                                    12

      C. Effect   of   the   2004   Amendments.        The commissioner

concluded the amended section 85.34 did not alter the fresh-start rule in

cases involving successive injuries resulting in industrial disability

sustained in the course of employment with different employers. Noting

new section 85.34(7)(b) established a formula for apportioning disability

only for successive work-related injuries sustained while working for the

same employer, the commissioner determined Roberts’s liability for

permanent partial disability benefits in this case cannot be apportioned

to account for any disability Billick sustained as a result of his injuries

sustained in 1985 and 1993 while working for other employers.

      The district court rejected the commissioner’s interpretation

limiting apportionment to instances of successive injuries sustained

while working for the same employer. The court acknowledged that the

2004 amendments did not completely abrogate the fresh-start rule,

noting that “[e]ach and every time a worker enters the competitive labor

market and obtains a new wage—whether higher or lower than the prior

wage—the worker . . . necessarily establishes a new baseline earning

capacity.” However, the court concluded the commissioner’s formulation

of the modified fresh-start rule erroneously exposed Roberts to liability—

in violation of section 85.34(7)(a)—for disability arising from injuries

sustained by Billick in 1985 and 1993 while working for different

employers. See Iowa Code § 85.34(7)(a) (“An employer is not liable for

compensating an employee’s preexisting disability that arose out of and

in the course of employment with a different employer . . . .”).       The

commissioner’s failure to order apportionment, the court concluded,

exposed Roberts to liability for Billick’s double recovery of permanent

partial disability benefits—an outcome the general assembly sought to

avoid. See 2004 Iowa Acts 1st Extraordinary Sess. ch. 1001, § 20.
                                          13

       The district court concluded the new section 85.34(7)(a)—when

read in conjunction with the amendment of section 85.34(2)(u) 3—

unambiguously abrogated the full-responsibility rule and extended the

rule of apportionment to successive work-related injuries with different

employers. Concluding the commissioner’s industrial disability decision

did not reveal whether it apportioned Roberts’s liability for Billick’s loss

of earning capacity, the court remanded to the commissioner for findings

on Billick’s earning capacity before and after the injuries sustained while

working for Roberts.

       Our review of the discordant readings of the 2004 amendments

begins with the proposition that we presume “the legislature is familiar

with the holdings of this court relative to legislative enactments.” Mallory

v. Paradise, 173 N.W.2d 264, 266 (Iowa 1969); see also State v. Jones,

298 N.W.2d 296, 298 (Iowa 1980) (“The legislature is presumed to know

the state of the law, including case law, at the time it enacts a statute.”).

We have often indicated we presume the legislature was aware of our

decisions when it crafted new statutes.             See, e.g., Simbro v. Delong’s

Sportswear, 332 N.W.2d 886, 889 (Iowa 1983) (“We assume that at the

time the legislature amended [section 85.34(2)(s)] it was familiar with the

existing case law that evaluated scheduled disability on a functional

basis.”); Beier Glass Co. v. Brundige, 329 N.W.2d 280, 285 (Iowa 1983)

(presuming the legislature was aware of our cases interpreting the word

“benefits” and the term “weekly compensation”). Thus, we presume the

general assembly knew the preexisting law pertaining to the fresh-start


       3Section 85.34(2)(u) bases compensation for permanent partial disability for
unscheduled injuries “caused by [work-related] disability” on diminution of “the earning
capacity . . . the employee possessed when the injury occurred.”             Iowa Code
§ 85.34(2)(u).
                                          14

and full-responsibility rules developed in Nelson, Celotex Corp., and

Venegas when it drafted and passed the 2004 amendments.                           This

presumption is most appropriate here because the statement of intent

accompanying the 2004 amendments expressly observed the enactment

was intended to modify the fresh-start and full-responsibility rules

announced in this court’s decisions.                  See 2004 Iowa Acts 1st

Extraordinary Sess. ch. 1001, § 20.

       At the time the 2004 amendments were adopted, the law applied

the fresh-start and full-responsibility rules to claims for permanent

partial unscheduled disability arising from successive work-related

injuries whether the injuries were sustained while working for the same

employer or for different employers.           Venegas, 638 N.W.2d at 701–02

(successive injuries with different employers); Celotex Corp., 541 N.W.2d

at 252, 256 (successive injuries with same employer).             Thus, the general

assembly was aware liability for successive work-related injuries was not

generally apportioned. 4 It is undisputed that the legislature intended to

modify the rules with the 2004 amendments. See 2004 Iowa Acts 1st

Extraordinary Sess. ch. 1001, § 20.             The fighting question presented

here, however, is the extent to which the amendments modified the
preexisting rules as they had developed and were applied in our caselaw.

       Upon review, we conclude the commissioner’s reading of section

85.34 as amended is correct.            We do not believe the amendment is

without ambiguity. One of the new sections reads, “An employer is not

liable for compensating an employee’s preexisting disability that arose

out of and in the course of employment with a different employer . . . .”

       4Apportionment     was permitted, however, for ascertainable portions of
permanent partial disability causally related to preexisting nonwork-related injuries or
conditions prior to the 2004 amendments. See Nelson, 544 N.W.2d at 264.
                                   15

Iowa Code § 85.34(7)(a). This might suggest that when an employee is

determined to have suffered a work-related industrial disability, any

resulting award of disability should be offset to account for any previous

work-related industrial disability sustained in the course and scope of

employment with, and compensated by, a previous employer. However,

the section does not expressly say that, and even more importantly, Iowa

Code section 85.34 provides no mechanism for apportioning the loss

between the present and previous employers. This is in direct contrast to

Iowa Code section 85.34(7)(b), which explains exactly how the offset is to

be calculated when an employee suffers successive injuries while

working for the same employer.     If the legislature wanted to require a

credit or offset of disability benefits in cases of successive unscheduled

injuries with different employers, it logically would have prescribed how

it should be determined.

      We also give considerable weight to the general assembly’s

statement of purpose when it adopted the 2004 amendments. See Iowa

Code § 4.6(7) (stating that we may rely on the legislature’s “preamble or

statement of policy” in interpreting an ambiguous statute); Taft v. Iowa

Dist. Ct., 828 N.W.2d 309, 317 (Iowa 2013).     In this case, the general

assembly’s statement of purpose was unmistakably clear.               The

legislature recognized that market forces “reevaluate[] a person as a

working unit each time the person competes in the competitive labor

market, causing a fresh start with each change of employment.” 2004

Iowa Acts 1st Extraordinary Sess. ch. 1001, § 20. We conclude therefore

the general assembly unmistakably reaffirmed the vitality of the fresh-

start rule in cases involving successive injuries in the course and scope

of employment with different employers.      With each fresh start, the

employee’s earning capacity is reset.   If a percentage of that refreshed
                                      16

earning capacity is subsequently lost as a consequence of a permanent

partial unscheduled injury, compensation for that percentage is owed.

The measure of such compensation is based on “the number of weeks in

relation to five hundred weeks as the reduction in the employee’s earning

capacity caused by the disability bears in relation to the earning capacity

that the employee possessed when the injury occurred.” Iowa Code

§ 85.34(2)(u). When a successive injury is sustained in the course and

scope of employment with a different employer, the earning capacity

possessed by the employee when the injury occurred is an earning

capacity refreshed by market forces when the new employment began.

      The notion underlying the 2004 amendments that a refreshed

earning capacity is established upon commencement of new employment

is based in part on the proposition that earning capacity is not static.

Physical    and   mental   injuries   sometimes   heal   over    time,    and

rehabilitation sometimes restores functional capacity, at least in part.

See Bearce v. FMC Corp., 465 N.W.2d 531, 536 (Iowa 1991) (finding the

claimant gained a fresh start because after a prior injury he rehabilitated

and improved his physical condition).       Further, postinjury education

sometimes     substantially   enhances     earning    capacity    prior    to

commencement of new employment.            Thus, the changing nature of

factors affecting a claimant’s postinjury earning capacity in the

competitive labor market is an essential feature of the rationale for the

modified fresh-start rule. See Excel Corp. v. Smithart, 654 N.W.2d 891,

898 (Iowa 2002) (“[A]n industrial disability is not a final indicator of the

degree to which a worker can use his or her body to earn wages, and it

does not consider the human capacity and spirit to overcome a disability

through rehabilitation, adjustments, simple perseverance, or other

methods.”).
                                          17

       We respectfully disagree with the district court’s conclusion that

the commissioner’s interpretation of the amendments—preserving the

fresh-start rule in cases of successive unscheduled injuries with different

employers—cannot be squared with the clear language of section

85.34(7)(a), which provides that “[a]n employer is not liable for

compensating an employee’s preexisting disability that arose out of and

in the course of employment with a different employer . . . .” Iowa Code

§ 85.34(7)(a). Under the modified fresh-start rule, the new employer is

not liable for disability arising out of unscheduled injuries sustained

during past employment with a former employer.                 The new employer’s

liability under section 85.34(2)(u) for permanent partial disability caused

by a successive injury is measured by comparing the claimant’s earning

capacity “when the injury occurred” with “the reduction in earning

capacity caused by the disability.”            Id. § 85.34(2)(u).       The earning

capacity when the injury occurred is a refreshed capacity provided by the

fresh-start rule. When, as a consequence of a successive work-related

injury, part of that refreshed earning capacity is lost, compensation is

owed under section 85.34(2)(u). See id. In this context, the fresh-start

rule holds the employer liable for a work-related permanent partial loss

of the new earning capacity refreshed by market forces and existing at

the time of the successive injury—not for a preexisting disability arising

from employment with a different employer. 5               Thus, we conclude the

commissioner did not err in determining the causal connection

requirement in section 85.34(2)(u) can be harmonized with the language

       5Under   this reading of section 85.34(7)(a), the subsection might be viewed as
unnecessary, since it restates what the law would be anyway. See Iowa Code § 4.4(2)
(setting forth the presumption that “[t]he entire statute is intended to be effective”).
However, for the reasons we have already explained, we think this reading is much
more logical and persuasive than the district court’s reading of the 2004 amendments.
                                       18

in section 85.34(7)(a) protecting employers from liability for disability

arising from employment with a different employer.

      The    district   court   also        concluded   the   commissioner’s

understanding of section 85.34—as amended by the 2004 enactment—

violated the general assembly’s purpose of preventing double recoveries

for successive work-related injuries.       We again disagree.   As we have

explained, the 2004 amendments preserve the fresh-start rule for an

employee sustaining successive injuries resulting in permanent partial

disability in the course of employment with different employers. Under

the rule, the injured employee recovers for a permanent partial loss of a

fully refreshed earning capacity redefined by market forces at the time

new employment began—not for an additional loss of whatever earning

capacity may have been extant prior to commencement of the new

employment. In this sense, the employee’s recovery for a successive loss

of earning capacity sustained in the employment with a new employer is

not a double recovery for a prior loss. It is instead a full recovery of that

which has been lost as a consequence of the successive injury: a

percentage of the refreshed earning capacity.

      Under the interpretation of section 85.34 advanced by Roberts,

Billick’s recovery in this case would be reduced pro tanto, in an amount

equal to 425 weeks of compensation he received for the 1985 and 1993

injuries sustained while working for former employers.        We reject that

interpretation because it is inconsistent with the fresh-start rule and

because it assumes earning capacity is static—an assumption we have

rejected above.    Moreover, the pro-tanto-reduction approach Roberts

advocates would not credit increases in earning capacity resulting from

restoration of physical capacity, education, training, or work experience

achieved prior to commencement of new employment with a different
                                   19

employer and a successive injury. Indeed, if section 85.34(7)(a) required

apportionment for successive unscheduled permanent partial disabilities

sustained while working for different employers, no employee could ever

actually gain a fresh start. The legislature intended to modify the fresh-

start rule, not eliminate it. 2004 Iowa Acts 1st Extraordinary Sess. ch.

1001, § 20.

        “We determine legislative intent from the words chosen by the

legislature, not what it should or might have said.”    Auen v. Alcoholic

Beverages Div., 679 N.W.2d 586, 590 (Iowa 2004).           If the general

assembly had intended to eliminate the fresh-start rule and require

apportionment of successive injuries producing permanent partial

disability in the course and scope of employment with different

employers, we think it would have said so.     See Hook v. Trevino, 839

N.W.2d 434, 443–44 (Iowa 2013) (“If the legislature had intended

volunteer immunity to apply to the state, it presumably would have said

so expressly, as it did for the emergency response immunity in the

Municipal Tort Claims Act.”); Iowa Med. Soc’y v. Iowa Bd. of Nursing, 831

N.W.2d 826, 841 (Iowa 2013) (“If the legislature had intended to give

another agency or organization the power to determine recognition by the

medical profession, it would have said so . . . .”).   Instead, the 2004

amendments to section 85.34 prescribed a formula for apportioning only

disability arising from successive injuries in the course and scope of

employment with the same employer.        Notably, the general assembly

disavowed any intent to change chapter 85 except as expressly provided

in the amendments. 2004 Iowa Acts 1st Extraordinary Sess. ch. 1001,

§ 20.    Accordingly, we conclude the commissioner correctly rejected

Roberts’s apportionment claim in this case.
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      V. Conclusion.

      The commissioner correctly concluded the legislature’s 2004

amendments did not modify the fresh-start rule for claimants sustaining

successive work-related unscheduled injuries with different employers.

Because Billick gained a fresh start when he began his employment with

Roberts in 2001, Roberts is not entitled to apportion its liability for

permanent partial disability benefits in this case.   The district court’s

contrary interpretation of section 85.34 was erroneous. Accordingly, we

reverse the district court’s ruling and remand the case to the district

court with instructions to affirm the commissioner’s appeal decision.

      REVERSED AND REMANDED WITH INSTRUCTIONS.
