
685 N.E.2d 992 (1997)
292 Ill. App.3d 558
226 Ill.Dec. 537
Stanislaw TRUSZEWSKI, Plaintiff-Appellee,
v.
OUTBOARD MOTOR MARINE CORP. and Lester Engineering Co., Defendant-Appellees.
OUTBOARD MOTOR MARINE CORP. and Lester Engineering Co., Third-Party Plaintiffs-Appellees,
v.
MUTUAL MAINTENANCE CO., Third-Party Defendant-Appellant.
Nos. 1-95-0059, 1-95-1756.
Appellate Court of Illinois, First District, Third Division.
September 24, 1997.
*993 William F. DeYoung, Loretto M. Kennedy and Carole C. Tubbesing of Burke, Weaver & Prell, Chicago, for Third-Party Defendant-Appellant.
Francis William Golden, Chicago, for Third-Party Plaintiffs-Appellees.
Justice LEAVITT delivered the opinion of the court:
Truszewski, who worked for Mutual Maintenance Co. (Mutual), sued Outboard Motor Marine Corp. (Outboard) and Lester Engineering Co. (Lester) for damages resulting from an injury to his hand which occurred while Truszewski cleaned a machine manufactured by Lester and owned and operated by Outboard. Truszewski received $387,500 in a settlement, $287,500 of which originated with Outboard and $100,000 of which originated with Lester. As part of a settlement, Outboard and Lester dismissed with prejudice their contribution claims against each other. In the remaining contribution action where Outboard sued Mutual, a jury found Mutual responsible for 40% of Outboard's liability to Truszewski. The judge ordered Mutual to pay Outboard $115,000, representing 40% of $287,500. We reverse and remand.
Mutual claims the trial court erred when it rejected Mutual's proffered jury verdict form which read:


"We, the jury, apportion responsibility as follows:
Outboard Marine Corporation  ___%
Mutual Maintenance Company   ___%
Lester Engineering           ___%
Total:                       100%."

Instead, the court submitted the verdict form suggested by Outboard which read:


"We, the jury, apportion responsibility as follows:
Outboard Marine Corporation  ___%
Mutual Maintenance Company   ___%
Total:                       100%."

Trial courts have discretion to decide which jury instructions to deliver. Gaines v. Townsend, 244 Ill.App.3d 569, 576, 184 Ill.Dec. 479, 613 N.E.2d 796 (1993). We will grant a new trial only where a party shows it suffered serious prejudice to its right to a fair trial due to the court's failure to give a tendered jury instruction. Gaines, 244 Ill.App.3d at 576, 184 Ill.Dec. 479, 613 N.E.2d 796.
Both parties accurately state the axiom "when available, the Illinois Pattern Jury Instruction [IPI] should be given, unless the court determines that it does not accurately state the law." Harnischfeger Corp. v. Gleason Crane Rentals, Inc., 223 Ill.App.3d 444, 465, 165 Ill.Dec. 770, 585 N.E.2d 166 (1991). The IPI applicable here is 600.16, which reads:
"Verdict FormApportionment of ResponsibilityContribution Following Settlement:
We, the jury, apportion responsibility as follows:


________________________________________ ___%
name of contribution plaintiff
________________________________________ ___%
name of first contribution defendant
________________________________________ ___%
name of second contribution defendant
________________________________________ ___%
name or describe non-party
TOTAL                                    100%

If you find that any person or entity was [not negligent] [not at fault] in a way that proximately caused the injured person's *994 injury, then you should enter a zero as to that person or persons.
"The "Notes on Use" which follow IPI 600.16 state "* * * this verdict form makes provision for determining the fault attributable to non-parties. The trial judge, after verdict, will then have to determine the contribution judgment to be entered." Illinois Pattern Jury Instructions, Civil, No. 600.16 (3d ed.1993).
Mutual claims the verdict form selected by the court unjustifiably deviated from the relevant IPI. Mutual asserts the instruction utilized did not accurately conform to the law of contribution embodied in Illinois' Joint Tortfeasor Contribution Act [the Contribution Act]. 740 ILCS 100/0.01(West 1992). The Contribution Act provides:
"(a) * * * where 2 or more persons are subject to liability in tort arising out of the same injury to person or property, * * * there is a right of contribution among them, even though judgment has not been entered against any or all of them.
(b) The right of contribution exists only in favor of a tortfeasor who has paid more than his pro rata share of the common liability, and his total recovery is limited to the amount paid by him in excess of his pro rata share. No tortfeasor is liable to make contribution beyond his own pro rata share of the common liability." 740 ILCS 100/2.
Although not defined in the Contribution Act, the terms "pro rata" and "common liability" are defined in the introduction to the contribution section of the Illinois Pattern Jury Instructions for Civil Cases. It reads:
"`Pro rata' as used in [740 ILCS 100/2(b) (1994)] merely means the percentage share as assessed by the trier of fact. `Common liability' [under section 2(b) ] means the total sum of the liability of all persons who contributed as a cause to the plaintiff's injury, no matter how small each share of that liability might be." Illinois Pattern Jury Instructions, Civil, No. 600.00 (3d ed.1993), citing Ziarko v. Soo Line Railroad Co., 234 Ill.App.3d 860, 176 Ill. Dec. 698, 602 N.E.2d 5 (1992), and Mallaney v. Dunaway, 178 Ill.App.3d 827, 831, 128 Ill.Dec. 26, 533 N.E.2d 1114 (1988).
Our supreme court recognized that the Contribution Act is concerned with the relative culpability of defendants. Doyle v. Rhodes, 101 Ill.2d 1, 14, 77 Ill.Dec. 759, 461 N.E.2d 382 (1984). It provides a remedy for an entity that has paid more than its pro rata share of the common liability by allowing it to seek contribution from a fellow joint tortfeasor who has not paid his pro rata share of the common liability. 740 ILCS 100/2. The Contribution Act also establishes a remedy for a joint tortfeasor from whom contribution is sought. He cannot be made to pay more than his pro rata share of the common liability. 740 ILCS 100/2. And, one seeking contribution can only recover the amount he paid in excess of his pro rata share. Lilly v. Marcal Rope and Rigging, 289 Ill.App.3d 1105, 224 Ill.Dec. 920, 927, 682 N.E.2d 481, 488 (1997).
Mutual specifically alleges the verdict form, by failing to apportion fault among all three joint tortfeasors, caused Mutual to pay more than its pro rata share of the common liability in violation of the Contribution Act. 740 ILCS 100/2. Common liability here means the total sum of Mutual's, Outboard's and Lester's liability, no matter how small or how great each share might be. Illinois Pattern Jury Instructions, Civil, No. 600.00 (3d ed.1993).
Although no case squarely confronts the question whether excluding a non-party tortfeasor's fault on a verdict form causes an unfair determination of a party's pro-rata share under the Contribution Act, Mutual directs us to Gordon Broom's The IDC Monograph: Instructing the Jury on Contributory Negligence, Contribution, and Apportionment in the Multiple Joint Tortfeasor Case, Illinois Defense Counsel Quarterly, Vol. 4, No. 2, pp. ii-xxiv (1994), which supports its position. The author there asserts where only two of three parties who contributed to plaintiff's injury are listed on a verdict form, "the total pro-rata fault of the parties as to each other will equal 100%, [however,] that is only 100% of the common liability of the parties left in the case, not 100% of common liability `of all persons who contributed' to plaintiff's injury." The IDC *995 Monograph, IDC Quarterly at viii. And, under Illinois' Contribution Act, a joint tortfeasor can only be made to contribute his pro rata share of "the total sum of the liability of all persons who contributed as a cause to the plaintiff's injury." Illinois Pattern Jury Instructions, Civil, No. 600.00 (3d ed.1993).
Outboard claims Harnischfeger, 223 Ill. App.3d 444, 165 Ill.Dec. 770, 585 N.E.2d 166, supports its position that the verdict form used here was proper. In Harnischfeger, John Clark was injured when the crane he operated for Keeley & Sons contacted an energized power line. Clark sued Keeley Brothers Contracting Co., Keeley & Sons, Harnischfeger, H.H. Hall Construction Company [Hall], Union Electric Company [Union], and Gleason Crane Rentals, Inc. [Gleason]. Clark settled with Harnischfeger, Hall and Union. As part of the settlement, Clark's claims against Gleason were dismissed. Harnischfeger, Hall and Union, none of which had claims against each other, then tried their contribution actions together against Gleason. The court utilized the third-party plaintiffs' suggested verdict forms which read:
"As between Harnischfeger Corporation and Gleason Crane Rentals, Inc., we, the jury, apportion damages as follows:


Harnischfeger Corporation       ___%
Gleason Crane Rentals, Inc.     ___%
TOTAL                           100%

As between H.H. Hall Construction Company and Gleason Crane Rentals, Inc., we, the jury, apportion damages as follows:


H.H. Hall Construction Company  ___%
Gleason Crane Rentals, Inc.     ___%
TOTAL                           100%

As between Union Electric Company and Gleason Crane Rentals, Inc., we, the jury, apportion damages as follows:


Union Electric Company          ___%
Gleason Crane Rentals, Inc.     ___%
TOTAL                           100%."

The appellate court held the verdict forms were proper, stating: "Gleason's claim that the single verdict form would have reduced its obligation is simply unsupported." Harnischfeger, 223 Ill.App.3d at 462, 165 Ill.Dec. 770, 585 N.E.2d 166.
We find the decision in Harnischfeger distinguishable from the case sub judice. Harnischfeger did not involve a non-party tortfeasor and it was tried prior to the 1993 revision of IPI 600.16 to its current form. The former 600.16 did not dictate non-parties' inclusion, as the current version does. The old section read:
"600.16 Verdict FormApportionment of Responsibility
We, the jury, apportion damages as follows:


_______________________  ___%
name of party
_______________________  ___%
name of party
_______________________  ___%
name of party
TOTAL:                   100%."

Illinois Pattern Jury Instructions, Civil, No. 600.16 (August 1986) Supp. pg. 600-38.
More importantly however, we find that decision's logic fundamentally flawed. Harnischfeger settled by paying the plaintiff $1,700,000. Hall paid $2,000,000 and Union paid $500,000 to Clark. Based on the aforementioned verdict form, the jury assessed fault:


Harnischfeger Corp.                 50%         $ 850,000
Gleason Crane Rentals, Inc.         50%         $ 850,000
______________________________     _____       ___________
                                    100%        $1,700,000
H.H. Hall Construction Co.            5%        $  100,000
Gleason Crane Rentals, Inc.          95%        $1,900,000
______________________________      _____      ____________
                                     100%       $2,000,000
Union Electric Co.                    10%       $   50,000
Gleason Crane Rentals, Inc.           90%       $  450,000
______________________________      _____      _____________
                                     100%       $  500,000

Based on the verdict form, Gleason ultimately contributed $3,200,000, or approximately 76.2% of the total amount paid to the plaintiff.
That result patently violated the Contribution Act which states that no tortfeasor is liable to make contribution beyond his pro rata share of the common liability. 740 ILCS 100/2(b). Although the jury did not calculate Gleason's pro rata share of the common liability, that share can be algebraically deduced from the jury's assessments. The IDC Monograph, IDC Quarterly, at xii-xiv. That article articulately sets forth a mathematical equation which yields each party's fault percentage:
"The common fault of Harnischfeger (A), H.H. Hall (B), Union (C) and Gleason (D) equaled 100% of the common liability.

*996 Thus, the first part of the equation for each defendant's percentage of fault sets up as follows:
   A + B + C + D = 100%
Using the jury's calculation of each settling tortfeasor's fault compared to that of D, the equation sets up as follows:
A and D were found to have contributed equally to the injury, i.e. 50%/50%.
   A = D.
B's fault compared to D's fault was 5%.
   B = 5% and D = 95%
   or
   B = 1/19D.
C's fault compared to D's fault was 10%.
   C = 10% and D = 90%
   or
   C = 1/9D.
Substituting these new equations for A, B, and C, the equation for the percentages of fault for A, B, C and D combined is now:
   D + 1/19(D) + 1/9(D) + D = 100%.
The common denominat[or] for the equation is 171, which converts this equation as follows:
   171(D) + 9(D) + 171(D) = 17,100.
D's percentage can now be computed:
   370(D) = 17,100.
   D = 46.215% [rounded]."
So, Gleason was 46.215% at fault, Hall was 2.43% at fault, Union was 5.14% at fault and Harnischfeger was 46.215% at fault. Gleason's pro rata share of the common liability was thus not 76.2%, but rather 46.215%.
The settlement with the plaintiff dictated the universe of common liability which was $4,200,000. The Contribution Act mandated Gleason pay no more than its pro-rata share of the common liability, 46.215%. 740 ILCS 100/2. That sum was $1,941,030, not $3,200,000 which the court mandated Gleason contribute based on the ill-conceived verdict forms. Harnischfeger, 223 Ill.App.3d at 462, 165 Ill.Dec. 770, 585 N.E.2d 166.
Again, the issues in Harnischfeger are distinguishable from those sub judice. We reject Outboard's suggestion that we adopt the logic employed in that decision. We use Harnischfeger only to illustrate the gross inequity an improvidently drawn verdict form can yield.
Outboard further argues the Contribution Act bars Lester's inclusion on the verdict form based on the following language:
"The tortfeasor who settles with a claimant [in good faith] is discharged from all liability for any contribution to any other tortfeasor." 740 ILCS 100/2(d).
This language does not support Outboard's contention.
The Contribution Act provides a defendant who enters into a good faith settlement has no further liability. Lester's was a good faith settlement, and Lester was therefore discharged from liability for contribution. Accordingly, Lester's presence on the jury form could not have caused Lester to pay again. A jury's assessment of Lester's pro rata share of common liability would serve only to facilitate its assessment of Mutual's pro rata share.
Lester's presence on the verdict form is not only non-prejudicial to Lester, but also essential to a just resolution of this third-party dispute. Because a party cannot be forced to pay more than his pro rata share of the common liability, and because the common liability here is the sum of Lester's, Mutual's and Outboard's fault (a percentage that must equal 100), Mutual's pro rata share of the common liability cannot be fairly assessed without reference to Lester's pro rata share. 740 ILCS 100/2(b).
In reaching our conclusion, we are aware that no Illinois court has directly addressed the issue before us today. However, in a related context, this court held similarly. In Bofman v. Material Service Corp., 125 Ill. App.3d 1053, 1063-64, 81 Ill.Dec. 262, 466 N.E.2d 1064 (1984), the comparative negligence instruction under review required the jury to consider the negligence of "all other persons" in computing "total combined negligence." Bofman, 125 Ill.App.3d at 1063, 81 Ill.Dec. 262, 466 N.E.2d 1064. We held "consideration of both parties and nonparties to an action is essential for determining liability commensurate with degree of total fault." *997 Bofman, 125 Ill.App.3d at 1064, 81 Ill.Dec. 262, 466 N.E.2d 1064.
In sum, IPI 600.16 called for the inclusion of the non-party joint tortfeasor, Lester. The court was required to use that instruction unless it determined IPI 600.16 did not accurately state the law. Without expounding its rationale, the court deviated from IPI 600.16. For this reason and those enounced previously, the trial court erred when it rejected the verdict form tendered by Mutual and utilized the one submitted by Outboard. Because that error tainted the fairness of this trial, a new one should be allowed.
REVERSED AND REMANDED.
COUSINS, P.J., and GORDON, J., concur.
