                            In the

United States Court of Appeals
              For the Seventh Circuit

No. 07-2968

G ERALD O VERMAN,
                                              Plaintiff-Appellant,
                                v.

M ICHAEL J. A STRUE,
                                             Defendant-Appellee.


           Appeal from the United States District Court
               for the Western District of Wisconsin.
           No. 06 C 484—Barbara B. Crabb, Chief Judge.



       A RGUED JULY 9, 2008—D ECIDED O CTOBER 7, 2008




  Before P OSNER, S YKES, and T INDER, Circuit Judges.
  P ER C URIAM. Gerald Overman applied for Social Security
disability insurance benefits and supplemental security
income payments, claiming that he was unable to work
due primarily to fatigue related to Graves’ disease, anemia,
and vision problems. After conducting a hearing an
Administrative Law Judge (“ALJ”) denied benefits,
relying on testimony by a vocational expert (“VE”) to find
that, though Overman could not return to his past work,
he could perform a significant number of other available
2                                                No. 07-2968

jobs. On review by the district court, the court found that
substantial evidence supported the ALJ’s conclusion. In
this appeal, Overman challenges the ALJ’s reliance on the
VE’s testimony. We will discuss the record that was
before the ALJ prior to addressing those contentions.
  Overman, currently 58 years old, is a high-school gradu-
ate. For fifteen years before the alleged onset of disability,
he worked at a resort. His duties included maintaining
and repairing the golf course irrigation system, setting
up for conventions, and performing other small repairs. In
2003 Overman began to feel overheated, shaky, and
fatigued on a regular basis, and he experienced a rapid,
unexplained weight loss of more than 70 pounds. In
November of that year, Overman—who already suffered
from diabetes, hypertension, glaucoma, cataracts, and
severe myopia—quit his job because he was too fatigued
to continue working.
   Overman reported his symptoms to his treating physi-
cian, Dr. John McKevett, and was referred to an endocri-
nologist who diagnosed Overman with Graves’ disease, a
form of hyperthyroidism that may cause weight loss,
tremulousness, and weakness, among other symptoms.
S TEDMAN’S M EDICAL D ICTIONARY 557, 928 (28th ed. 2006).
Graves’ disease is chronic, but the symptoms are treat-
able. See MayoClinic.com, Graves’ Disease (July 6,
2007), http://www.mayoclinic.com/health/graves-disease/
DS00181/DSECTION= treatments-and-drugs. He also
was diagnosed with anemia, which frequently causes
fatigue and lethargy in its sufferer. STEDMAN’S M EDICAL
D ICTIONARY at 78.
No. 07-2968                                              3

  Overman began radioactive iodine therapy for his
Graves’ disease in late December 2003. He filed his ap-
plication for benefits shortly thereafter. The therapy
initially alleviated some of Overman’s symptoms, but
then instead of producing too much thyroid hormone,
Overman began producing too little, a condition called
hypothyroidism, which (like hyperthyroidism) often
causes fatigue and muscle weakness. S TEDMAN’S M EDICAL
D ICTIONARY at 939, 1277. (Roughly 70% of patients treated
with radioactive iodine experience this overcorrection of
thyroid function, after which they usually require lifelong
thyroid hormone replacement therapy.) Endocrinologists
tested Overman’s thyroid function every four to eight
weeks throughout 2004 and sent the results to Dr.
McKevett, who prescribed a thyroid-hormone replace-
ment drug called Synthroid. After taking Synthroid for
two weeks, Overman told Dr. McKevett that he still tired
easily but his energy level was “slowly but surely im-
proving.” At the same visit, the doctor noted “moderate
generalized weakness,” but stated that this was also
“slowly improving.” Dr. McKevett’s records reflect that
Overman’s dosage of Synthroid was adjusted several
times over the next 18 months. But by the end of that
period, Dr. McKevett still had not determined the
correct dosage and attributed Overman’s continued fatigue
to “not being conditioned” to the medication. As for
Overman’s anemia, the records do not mention any
treatment for that ailment, and Overman did not know
at the time of his hearing whether he was still anemic.
  Overman also submitted records from his optometrist
and opthalmologist concerning his vision problems. The
4                                               No. 07-2968

opthalmologist reported that Overman suffered from
“pathologic myopia,” glaucoma, and cataracts. He said that
Overman’s visual acuity of 20/80 made “any visual task
difficult” and his eyesight would continue to deteriorate.
His optometrist reported that Overman had “open angle”
glaucoma and myopic degeneration resulting in “poor
vision in general” and “almost no night vision.” Both
doctors agreed that Overman’s vision would likely
worsen over time. The medical records show that Over-
man’s diabetes and hypertension were, for the most part,
well-controlled during the alleged period of disability.
   At the hearing before the ALJ in November 2005, Over-
man testified that he was still taking Synthroid for his
thyroid condition but that his doctor had not yet deter-
mined the correct dosage. He also testified that he took
medication for his diabetes but was not insulin-dependent.
He said that he was nearsighted, wore glasses, and could
watch TV as long as he was within five feet of the set.
Regarding his daily activities, Overman testified that he
tries to do things around the house but finds it very
tiring and that, during the six months prior to the hearing,
if he sat down in a chair for more than five minutes he
would fall asleep. Overman testified that he could feed
and bathe himself and that his performance of household
chores did not significantly change after the onset of
disability in November 2003. He said that he could drive
during the day but not after dark as he had “no night
vision.” He also said that he could walk a half mile on
flat terrain as long as it was not too cold out, but that in
the cold his extremities go numb due to his diabetes. He
said that the numbness had worsened over time and was
No. 07-2968                                               5

not always associated with cold temperatures. Finally,
Overman testified that his resort maintenance job had
been unskilled and primarily required making small
repairs to door knobs, light switch covers, and the like. He
left the job in November 2003 after fainting at work. He
said that he would not be able to return to that job be-
cause he could not tolerate working outdoors in hot
weather and because he was routinely required to lift
more weight than Dr. McKevett recommended.
  Dr. Julianne Koski, a family practitioner and agency
consultant, also testified at the hearing. Having reviewed
Overman’s medical records, Dr. Koski concurred that
Overman suffered from Graves’ disease, severe myopia
with glaucoma, diabetes, and hypertension. She testified
that it was difficult to determine Overman’s corrected
visual acuity from his medical records, but she guessed
that it was no better than 20/100 when corrected with
glasses. She also concurred that he suffered from cataracts,
which, in her opinion, were not yet “visually significant.”
Dr. Koski opined that none of Overman’s impairments
met or equaled Social Security medical listings, so she
analyzed how, in her view, his ailments impacted his
residual functional capacity. She said that Overman could
not perform work requiring fine discrimination or signifi-
cant reading, should stay away from hazards and extreme
temperatures, should avoid all ropes and scaffolding
and climb ladders only occasionally, should never lift
more than fifty pounds but could lift twenty pounds “on
a more frequent basis,” and should not do any repetitive
over-the-shoulder lifting. She did not recommend any
limitations on Overman’s ability to sit or stand.
6                                              No. 07-2968

  The last witness at the hearing was the vocational expert
(“VE”), Kenneth Ogren. The ALJ asked the VE, hypotheti-
cally, whether a person with a residual functional capacity
as described by Dr. Koski—including the limitations on
reading, fine discrimination, and extreme tempera-
tures—could do any of Overman’s past relevant work. The
VE answered that the extreme-temperatures limitation
ruled out Overman’s prior work, much of which was
performed outdoors. The ALJ then asked, hypothetically,
whether there were other jobs in the region that a person
with those same limitations could perform. The VE an-
swered that such a person could perform two occupations:
“hand packager, and that is at DOT 920.587-018. . . . [and]
Rack room worker, 920.665-014.” A “hand packager”
manually packages materials and products, and a “rack-
room worker” tends machines that fill metal kegs with beer
in the keg-filling (or racking) room of a brewery; both
positions require a “medium” level of exertion. See D EP’T
OF L ABOR , D ICTIONARY OF O CCUPATIONAL T ITLES 932-33
(4th ed. rev. 1991), available at http://www.oalj.dol.gov/
libdot.htm. According to the VE, there were 1,200 and 800
such jobs, respectively, available in Minnesota. (The dis-
trict court rejected Overman’s argument that the VE
should have used a Wisconsin rather than a Minnesota
database to evaluate the number of available jobs, but
Overman does not renew that argument on appeal.)
Finally, the ALJ asked the VE whether his testimony was
consistent with the Dictionary of Occupational Titles
(“DOT”), and the VE answered “yes.”
  Overman’s counsel then cross-examined the VE as
follows:
No. 07-2968                                              7

   Counsel: And then if you assume a person couldn’t
   do, couldn’t do close up work because of finger
   problems, hand problems, that sort of thing, would
   that change your opinion on this?
   VE: Yes.
   Counsel: How would it change it?
   VE: It would eliminate the two jobs.
   Counsel: Pardon me?
   VE: It would eliminate both occupations.
   Counsel: And why is that?
   VE: Basically you have to have at least some vision
   to do the packaging I’m talking about and some
   vision to hang articles on racks.
   Counsel: And as I understand the doctor, she was
   saying he could do things with gross discrimina-
   tion, but he couldn’t do it with the fine discrim-
   ination?
   VE: Yes. That’s the way I understood it too.
   Counsel: And as I understand it, that means, and
   correct me if I’m wrong, he can’t work up close
   because he can’t really see his hands, is that it?
   VE: I guess the way I interpreted that is that he
   couldn’t do like small assemblies and things like
   that, smaller type work.
   Counsel: Uh-huh. But we’re talking about packag-
   ing of objects into a box then versus actual fine
   manipulation?
8                                                No. 07-2968

    VE: Yes.
    Counsel: Then I guess it’s a matter of degree, isn’t
    it.
    VE: Yes.
    Counsel: So those may well be eliminated as well?
    VE: The smaller parts, yes.
    Counsel: By the fact that he’s sitting there trying to
    do things close up, right?
    VE: Exactly.
    Counsel: All right. And I suppose I would have to,
    that would also get in to the issue of what’s on the
    labeling and how you would package it and how it
    would have to be packaged, that sort of thing.
    VE: If he had to read to do it, I would say those
    jobs would be eliminated, yes.
    Counsel: So then there would be no jobs in the
    national economy, if you assume he couldn’t do it
    because it was close work?
    VE: Yeah, I eliminated those possibilities already.
  In determining that Overman was not disabled, the ALJ
performed the usual five-step sequential analysis. See
20 C.F.R. §§ 404.1520, 416.920. According to the ALJ,
Overman had not engaged in substantial work since his
claimed onset date, and he was severely impaired, but
none of his impairments were severe enough to presump-
tively preclude gainful work. See id. § 404, subpt. P, app. 1.
The ALJ then found that Overman could perform work
No. 07-2968                                                 9

of “medium” exertion with limitations virtually identical
to those described at the hearing by Dr. Koski, including
gross but not fine discrimination, no significant reading
tasks, and no extremes of cold or heat. The ALJ concluded
that these limitations would preclude Overman’s past
relevant work. However, the ALJ found that Overman
was not disabled at step five because he could work as
a hand packager or a rack-room worker. The ALJ stated
that, in reaching this conclusion, he gave “great weight” to
the VE’s testimony, which the ALJ found “credible,
persuasive, and consistent with the record as a whole.” The
ALJ also noted that the VE had confirmed that his testi-
mony was consistent with the DOT. As for the VE’s
testimony on cross-examination, the ALJ did not
interpret his statements to suggest that Overman’s limita-
tions would prevent him from working as a hand packager
or rack-room worker. Rather, under the ALJ’s reading
of the testimony, the VE simply explained that he had
previously eliminated from consideration jobs requiring
the type of small assembly work and reading that
Overman is unable to do before arriving at the conclusion
that there were some 2,000 jobs in Minnesota available
to Overman despite his limitations.
  The Appeals Council denied Overman’s request for
review, making the ALJ’s ruling the Commissioner’s final
decision. See, e.g., Schmidt v. Astrue, 496 F.3d 833, 841 (7th
Cir. 2007). Overman sought review in the district court,
see 42 U.S.C. § 405(g), and, as noted, the district court
upheld the ALJ’s decision. And now we address the
claims of error that Overman raises in this appeal.
10                                               No. 07-2968

   We review the ALJ’s decision deferentially, upholding it
if it is supported by substantial evidence. Skinner v. Astrue,
478 F.3d 836, 841 (7th Cir. 2007). “Evidence is ‘substantial’
if it is sufficient for a reasonable person to accept as
adequate to support the decision.” Jens v. Barnhart, 347 F.3d
209, 212 (7th Cir. 2003) (internal quotation marks and
citation omitted). “Although this standard is generous, it
is not entirely uncritical,” and the case must be remanded
if the decision lacks evidentiary support. Steele v. Barnhart,
290 F.3d 936, 940 (7th Cir. 2002). We view the record as a
whole but do not reweigh the evidence or substitute
our judgment for that of the ALJ. Schmidt v. Apfel, 201
F.3d 970, 972 (7th Cir. 2000).
  First, the VE’s testimony that Overman could work as a
hand packager or rack-room worker conflicts in several
respects with descriptions of those positions in the DOT.
Overman, according to the ALJ, must avoid extremes
of cold and heat, and his vision problems preclude both
fine discrimination and significant reading. A hand
packager, however, must deal with extreme heat “fre-
quently” (between one-third to two-thirds of the work-
day), and “near acuity”—clarity of vision at 20 inches or
less—is required “occasionally” (up to one-third of the
workday). See D EP’T OF L ABOR, S ELECTED C HARACTERISTICS
OF O CCUPATIONS D EFINED IN THE R EVISED D ICTIONARY
OF O CCUPATIONAL T ITLES 316, C-3 to C-4, D-1 (1993). For a
rack-room worker, near acuity is required frequently. See
id. at 316, C-3 to C-4. Both positions require workers to
read at a rate of 95-120 words per minute and to be able to
compare similarities and differences between words
and between series of numbers. See D EP’T OF L ABOR,
No. 07-2968                                              11

D ICTIONARY OF O CCUPATIONAL T ITLES at 932-33, 1010-11.
The Commissioner concedes on appeal that the VE’s
testimony conflicts with the DOT; the issue is whether
that conflict necessitates remand.
   Overman argues that (1) the ALJ violated Social Security
Ruling 00-4p by failing to require the VE to explain the
conflict, and (2) the VE’s flawed testimony cannot satisfy
the Commissioner’s burden at step five to prove that
Overman can perform other jobs despite his limitations.
Under SSR 00-4p, an ALJ has an “affirmative responsibil-
ity” to ask whether a vocational expert’s evidence “con-
flicts with information provided in the DOT” before
relying on that evidence to support a determination of
nondisability. SSR 00-4p at 4; see Massachi v. Astrue, 486
F.3d 1149, 1152-53 (9th Cir. 2007); Prochaska v. Barnhart,
454 F.3d 731, 735 (7th Cir. 2006). Here, the ALJ satisfied
this first step by asking the VE if his testimony was con-
sistent with the DOT; the VE answered (wrongly, as it
turns out) that it was. If evidence from a VE “appears to
conflict with the DOT,” SSR 00-4p requires further inquiry:
an ALJ must obtain “a reasonable explanation for the
apparent conflict.” SSR 00-4p at 5. It is here, Overman
argues, that the ALJ failed in his duty. Even though his
counsel never identified any apparent conflicts at the time
of the hearing, Overman argues that the discrepancies
between the DOT definitions and the VE’s testimony were
so obvious that the ALJ’s duty to investigate was triggered.
 The Commissioner counters that the conceded conflicts
were not obvious and that Overman forfeited any argu-
ment under SSR 00-4p because he did not raise it at the
12                                                No. 07-2968

hearing. For the latter proposition the Commissioner cites
Donahue v. Barnhart, 279 F.3d 441, 446-47 (7th Cir. 2002). But
we held more recently that because SSR 00-4p imposes
an affirmative duty on the ALJ to inquire into and resolve
apparent conflicts, a claimant’s failure to raise a possible
violation of SSR 00-4p at the administrative level does not
forfeit the right to argue later that a violation occurred. See
Prochaska, 454 F.3d at 735 (calling language to the contrary
in Donahue dicta). The Commissioner attempts to distin-
guish Prochaska by pointing out that in that case the ALJ
violated SSR 00-4p at the first step by never asking the
VE whether his testimony was consistent with the DOT.
But Prochaska makes clear that the ALJ’s affirmative duty
extends beyond merely asking the VE whether his testi-
mony is consistent with the DOT; the ALJ also must “elicit
a reasonable explanation for any discrepancy.” Prochaska,
454 F.3d at 735 (quoting Haddock v. Apfel, 196 F.3d 1084,
1087 (10th Cir. 1999)). Overman was denied the oppor-
tunity to appeal at the administrative level, and he raised
the SSR 00-4p issue before the district court, so he has not
forfeited the argument. See Prochaska, 454 F.3d at 735.
  Still, the failure of Overman’s counsel to identify the
conflicts at the time of the hearing is not without conse-
quence. Overman now has to argue that the conflicts were
obvious enough that the ALJ should have picked up on
them without any assistance, for SSR 00-4p requires only
that the ALJ investigate and resolve apparent conflicts
between the VE’s evidence and the DOT. SSR 00-4p;
see also, e.g., Prochaska, 454 F.3d at 735 (“If the
VE’s . . . evidence appears to conflict with the Dictionary of
Occupational Titles, the adjudicator will obtain a reason-
No. 07-2968                                             13

able explanation for the apparent conflict.” (emphasis
added)).
  Overman identifies two “apparent conflicts” in the VE’s
testimony that, in his view, the ALJ was required to
investigate further. After testifying on direct that
Overman could perform two occupations listed in the
DOT despite his limited vision and reading ability, the
VE contradicted himself on cross-examination, first by
saying that an inability to do “close up work” would
eliminate both jobs and second by saying that Overman
would be unable to work as a hand packager if that
position required reading. The Commissioner argues
that Overman’s counsel elicited these seemingly contra-
dictory statements by imposing alternate, more restrictive
hypothetical limitations than the ALJ had on direct.
According to the Commissioner, counsel’s question about
“close up work” introduced a limitation that Overman
lacked full use of his hands, which was not included
when the ALJ questioned the VE. But that argument is
undermined by the fact that the VE discussed visual
acuity rather than manipulative ability when he testified
that a limitation on “close up work” would eliminate both
jobs “because you have to have at least some vision.” The
Commissioner likewise attempts to reconcile the VE’s
statement that a reading limitation would preclude work
as a hand packager by suggesting that “the ability to
engage in significant reading was specifically excluded
from the ALJ’s hypothetical,” but that is incorrect. The
ALJ specified “no significant amount of reading tasks” in
his hypothetical questions on direct. The conflicts between
the VE’s supposedly DOT-based testimony on direct and
14                                              No. 07-2968

his statements on cross-examination, therefore, should
have been apparent to the ALJ. And it appears that per-
haps they were apparent, if not at the time of the hearing,
at least by the time the ALJ produced his ruling, in which
he attempts to rescue the testimony by interpreting the
statement that certain jobs would be eliminated as a
description of jobs the VE had previously eliminated
before reaching his conclusion that 2,000 jobs remained.
Whether that is or is not a plausible reading of the testi-
mony, the ALJ’s attempt to explain away the seemingly
contradictory statements is tantamount to an acknowl-
edgment that there were apparent discrepancies. The ALJ’s
reliance upon the VE’s testimony without developing the
record and obtaining a “reasonable explanation” for the
conflicts violated SSR 00-4p.
  Even if this was not the case, Overman also persuasively
argues that the ALJ’s ruling is not supported by substantial
evidence because it is premised on the VE’s “flawed”
testimony. The Commissioner bears the step-five burden
of establishing that the claimant can perform other work
that “exists in significant numbers in the national econ-
omy.” 20 C.F.R. § 404.1560(c)(2); see also Britton v. Astrue,
521 F.3d 799, 803 (7th Cir. 2008); Briscoe ex rel. Taylor v.
Barnhart, 425 F.3d 345, 352 (7th Cir. 2005). A VE’s testimony
can satisfy this burden only if that testimony is reliable.
Britton, 521 F.3d at 803; McKinnie v. Barnhart, 368 F.3d 907,
910 (7th Cir. 2004); Donahue, 279 F.3d at 446. “A finding
based on unreliable VE testimony is equivalent to a
finding that is not supported by substantial evidence
and must be vacated.” Britton, 521 F.3d at 803.
No. 07-2968                                               15

  The Commissioner argues that the ALJ was entitled to
rely on the VE’s testimony in spite of the later-identified
conflict with the DOT because an ALJ is permitted to give
VE testimony precedence over the DOT. In an appropriate
case this proposition would be correct, but it is not well
founded here. An ALJ is free to accept testimony from a
VE that conflicts with the DOT when, for example, the
VE’s experience and knowledge in a given situation
exceeds that of the DOT’s authors, Donahue, 279 F.3d at
446, or when the VE’s contrary testimony is based on
information in “other reliable publications,” SSR 00-4p. But
here the VE said that his testimony was consistent with
the DOT, so the Commissioner’s implicit suggestion
that the VE had some hidden knowledge that would
explain away the conflicts with the DOT is frivolous.
  Finally, the Commissioner argues that the ALJ’s reliance
upon the VE’s testimony is not reversible error because
an ALJ may rely on a VE’s “bottom-line” or “purely
conclusional” testimony, so long as the data and reasoning
underlying the opinion are “available on demand.”
Donahue, 279 F.3d at 446; see also Barrett v. Barnhart, 355
F.3d 1065, 1067 (7th Cir. 2004). In both Donahue and
Barrett, we ruled that an ALJ may rely on imperfect VE
testimony if a claimant does not question the basis for
the testimony at the time of the hearing. See Donahue,
279 F.3d at 446 (ruling that ALJ may rely on unchallenged
VE testimony that conflicted with DOT); Barrett, 355
F.3d at 1067 (ruling that ALJ may rely on unchallenged,
perfunctory VE testimony). According to the Commis-
sioner, the ALJ in this case was entitled to rely on the VE’s
“unchallenged” and “uncontradicted” testimony because
Overman never questioned its foundation.
16                                              No. 07-2968

  But Overman did challenge the VE’s testimony. Unlike in
Donahue and Barrett, Overman’s counsel cross-examined
the VE and elicited statements that seriously called into
question the reliability of the VE’s bottom-line conclusions.
Perhaps Overman’s inquiry into the basis for the VE’s
testimony could have been more thorough. But a disability
adjudication is “a hybrid between the adversarial and
inquisitorial models,” Donahue, 279 F.3d at 446, and if the
basis of the VE’s testimony is questioned at the hearing,
“then the ALJ should make an inquiry . . . to find out
whether the purported expert’s conclusions are reliable,”
id.; see also McKinnie, 368 F.3d at 911. No such inquiry was
performed here. Instead, the ALJ unquestioningly relied
on the VE’s bottom line, a bottom line later determined to
be in irreconcilable conflict with the DOT. There may be
additional work of which Overman is capable of perform-
ing, but the record does not support the conclusion that
he can perform either of the two positions identified by
the VE.
  The ALJ based his finding that Overman could perform
other work entirely on the VE’s erroneous testimony, and
that testimony is not “sufficient for a reasonable person
to accept as adequate to support the decision.” Jens, 347
F.3d at 212. Consequently, the ALJ’s disability determina-
tion is not supported by substantial evidence. See Boone v.
Barnhart, 353 F.3d 203, 206, 208-09 (3d Cir. 2003) (ruling
that VE’s testimony does not by itself provide substantial
evidence of claimant’s ability to perform significant
number of other jobs when testimony conflicts with DOT
and neither VE nor ALJ acknowledge or explain conflict);
Carey v. Apfel, 230 F.3d 131, 146-47 (5th Cir. 2000) (noting
No. 07-2968                                            17

that VE’s “erroneous characterization of the exertional
level or skills required to perform a particular job calls
into question both the probative value and reliability of
the expert’s testimony” and finding that ALJ may rely
upon such evidence only if “the record reflects an ade-
quate basis for doing so”). Because the ALJ’s ruling was
premised entirely on testimony that conflicted with the
DOT and otherwise was vague and confusing, this case
must be remanded for further proceedings.


                       Conclusion
  For the reasons stated above, the judgment of the
district court is R EVERSED and the case is R EMANDED for
further consideration by the agency.




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