### IN THE SUPREME COURT OF IOWA

No. 13

– 1009
Filed April 3 , 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 so ught 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 separ ate injuries
sustained while wor king for other employers. The w orkers’ compensation

c ommissioner concluded apportionment of industrial disability is not mandated by law under t he circumstances of this case. On judicial review, the district court conclude d the commissioner’s decision was based on a misinterpretat ion of amendments to our worker s ’ 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 com pany 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
worker s ’ compensation claim for these injuries was settled under Missouri law for an amount representing 18.5% permanent partial disability of the body as a who le.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 Bil lick 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 pla te. 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 d elivery 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 thor acic 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 super imposed on the chest injury he4

suffered earlier that day made Billick q uite distraught and produced a physical

– mental injury. Billick filed four workers’ compensation petitions against Roberts. The claims were consolidated for hearing. The commission er’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 th e 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 comp ensated 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 interpr etation 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 re levant 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 for5
permanent par tial 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 dete rmine 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 section s 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. Section s 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 the6 agency with authority to i nterpret 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 rev iew 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 se ction 85.34 did not modify the fresh

- start rule for an industrial disability claim made by a claimant who was prev iously 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 R oberts a credit for any disability compensated by previous employers would inflict upon him a n unwarranted reduction in benefits not intended by the legislature when it amended the Iowa Workers’ Compensation Act in 2004. Further, Billick suggests the dist rict court’s interpretation of the 2004 amendments circumvents the fundamental purpose and intent of Iowa Code c hapter
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).
Conver sely, 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 200 4 Iowa7 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 r uling 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 t he 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 preced ents,” 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 pre eminent 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 going8 beyond the other 50 percent of total. After having received the prior paym ents, 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 & Le x K. Larson, Larson’s Workers’ Compensation Law § 92.02[7][c], at 92

- 10 (r ev. 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 su bject to any active or dormant health impairments incurred prior to this employment.”). U nder 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 meas ured 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
fu nctional 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 p remise of a fresh start with respect to industrial disability” (emphasis added)). “W hen there are two successive
work

- related [unscheduled] injuries, the employer liable for the second injury ‘is generally held liable for the entire disability resulting f rom 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 context9 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 anothe r 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 disabil ity. 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 70 1. We agreed and held the
full

- responsibility rule shou ld 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 a ssembly held in 2004, two amendments to section
85.34 were ado pted. The first of these was an amendment to section 85.34(2)( u ), which provided as follows:

1 Prior to the 2004 amendments, w e 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 apportionme nt was necessary in Smithart because th e claimant was receiving worker s ’ 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 t he 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 shal l 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 th e 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 o f 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 emplo yer, 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 em ployee’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 e arnings 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

2 In our reproduction of this amendment, underlining indicates additions and strikethrough indicates deletions.11 for whi ch 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 e mployer 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 employm ent.
Id. § 11. The legislation included a statement of the general a ssembly’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 do uble 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 ann ounced by the Iowa [S]upreme [C]ourt in a series of judicial precedents.” Id. Yet, the statement notably revealed the general assembly did no t intend to eliminate the fresh

- start rule altogether. It instead recognized the c ontinuing vitality of the fres h

- 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 reevaluat es 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 g eneral a ssembly intended no change of existing law “t hat is not expressly provided” in the
enactment. Id.12

C. Effect of the 2004 Amendments. The commissioner
concluded the amended sectio n 85.34 did not alter the fresh

- start rule in cases involving successive injuries resulting in industrial disability
sust ained 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 determin ed 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 cou rt 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 no t completely abrogate the fresh

- start rule,
notin g 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 commi ssioner’s fo rmulation
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 conclu ded, exposed Roberts to liability for Billick’s double recovery of permanent partial disa bility benefits

— an outcome the general a ssembly sought to
avoid. See 2004 Iowa Acts 1st Extraordinary Sess. ch. 1001, § 20

.13

The district court concluded the new secti on 85.34(7)( a )

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

—

u nambiguously 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 l oss 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 propo sition 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 pr esumed 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 compens ation”). Thus, we presume the
g eneral assembly knew the pre exist ing law pertaining to the fresh

- start

3 Section 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 develo ped 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

w as intended to modify th e 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 ado pted, 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 699, 701

- 02 ( successive injuries with different employers); Celotex Corp. , 541 N.W.2d
at 252, 256 (successive injuries with same employer). Thus, the general

a ssembly was aware liability for successive work

- related injuries was not generally apportioned. 4 It is undi sputed 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 ru les as they had developed and were applied in our case law. 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 n ot liable for compensating an employee’s preexisting disability that arose out of and in the course of employment with a different employer . . . .”

4 Apportionment was permitted, however, for ascertainable portions of permanent partial dis ability causally related to pre existing nonwork

- related injuries or conditions prior to the 2 004 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

- r elated 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 sec tion 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 ex actly 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 g ive considerable weight to the general a ssembly’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

a ssembly’s statement of purpose was unmistakably clear. The legislature recogni zed 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 Extrao rdinary Sess. ch. 1001, § 20. W e conclude there fore
t he general a ssembly unmistakably reaff irmed 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 refreshed16 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 th e injury occurred.” Iowa Code § 85.34(2)( u ). When a successive injury is sustaine d in the course and scope of employment with a different employer, the earning capa city possessed by the employee w hen the injury occurred is an earning capacity refreshed by market forces when the new employment began. The notion underlying the 2004 amend ments 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 restore s functional capacity, at least in part.
See Bearce v. FMC Corp. , 4 6 5 N.W.2d 531, 536 (Iowa 1991) (finding the
claima nt 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
fact ors affecting a claimant’s post injury earning capacity in the competitive labor market is an essential feature of the rationale fo r 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 c apacity 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

— can no t 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 disabili ty that arose out of an d in the course of employment with a differe nt employer . . .

. ” Iowa Code § 85.34(7)( a ). Under the modified fresh

- st art 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 reductio n in earning capacity caused by the disability.” Id . § 85.34(2)( u ). The earning capacity w hen 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 refreshe d 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 exist ing 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 har monized with the language

5 Under 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 200 4 enactment

— violated t he general a ssembly’s purpose of preventing double recoveries
for successive work

- related injuries. We again disagree. As we have explained, the 200 4 amendments preserve the fresh

- start rule for an employee sustaining successive inj uries 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 ref reshed earning capacity redefined by market forces at the time

n ew 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 in jury: a percentage of the refreshed earning capacity. Under the interpretation of section 85.34 adv anced 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 rej ected above. Moreover, the pro

- tanto

- reduction approach Roberts advocates would not credit increases in earning capacity resulting from

r estoration of physical capacity, education, training, or work experience achieved prior to commencement of new employment with a different19 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 g en eral

a ssembly 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 Me d. 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

amen dments 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 a ssembly 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.20

V. Conclusion. The commissioner correctly concluded th e legislature’s 2004

amen dments 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, Rob erts 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 t o the district court with instructions to affirm the commissioner’s appeal decision.
REVERSED AND REMANDED WITH INSTRUCTIONS.