COMMUNICATIONS WORKERS OF AMERICA; AFL-CIO, CLC; FLORIDA POLICE BENEVOLENT ASSOCIATION, INC.; GAINESVILLE PROFESSIONAL FIRE FIGHTERS, IAFF, LOCAL 2157; AND GATOR LODGE 67, INC., FRATERNAL ORDER OF POLICE, APPELLANTS,

v.

CITY OF GAINESVILLE, FLORIDA, APPELLEE

BENTON, C.J.

Four labor unions representing employees of the City of Gainesville appeal a final order of the Public Employees Relations Commission (PERC) that rejected Hearing Officer Choppin’s ruling that the City had engaged in unfair labor practices, in violation of sections 447.501(l)(a) and (c), Florida Statutes (2008), by refusing to bargain over changes it made to health insurance benefits for city employees, once they retire. The parties’ collective bargaining agreements did not address the issue, so it was incumbent on the appellants to show that the City’s furnishing retirees’ health benefits amounted to an established past practice. Persuaded the hearing officer got it right, we reverse and remand to PERC for further proceedings.

The parties’ collective bargaining agreements do not discuss health insurance benefits for retirees. But the City has helped pay for such benefits for many years. In fact, until 1995 the City paid 100% of retirees’ health insurance premiums (for individual coverage) including all premium increases occurring after retirement. The City reduced the percentage in 1995, but continued to pay a fixed percentage of retirees’ insurance premiums, including the same fixed percentage of premium increases occurring after retirement.

The City effected the change in 1995 by adopting a city ordinance incorpo*1072rating the formula. Gainesville, Fla., Ordinance 4066 (Mar. 27, 1995). While the 1995 change the ordinance represented was not the product of collective bargaining, the unions waived no collective bargaining rights going forward by acquiescing in the change.1

*1073The ordinance, and the formula it embodied, remained unchanged until 2008, when the City adopted a superseding ordinance, again changing its method of contributing to retirees’ health benefits, this time by underwriting health insurance premiums up to a set dollar amount (rather than paying a percentage of the premiums). The 2008 change, which shifts to retirees the full amount (not merely a percentage) of any increase in premiums occurring in retirement, gave rise to the present controversy, and to unfair labor practice charges, because the City refused to bargain over the change.

When the unions filed unfair labor practice charges under sections 447.501(l)(a) and (c), Florida Statutes (2008), alleging the City’s refusal to bargain, a PERC hearing officer conducted an evidentiary hearing. Eventually, the hearing officer recommended that PERC find that the City had engaged in an unfair labor practice by unilaterally changing the health insurance benefits employees would receive as retirees, without negotiating the changes with the unions. PERC rejected the hearing officer’s recommendation, however, and dismissed the unfair labor practice charges. The unions then brought the present appeal.

Like PERC itself, we are “bound to honor a hearing officer’s findings of fact unless they are not supported by competent, substantial evidence.” City of Winter Springs v. Winter Springs Prof'l, 885 So.2d 494, 497 (Fla. 1st DCA 2004) (citing Belleau, v. Dep’t of Envtl. Prot., 695 So.2d 1305, 1307 (Fla. 1st DCA 1997)). In reviewing PERC’s decisions, moreover, we must not lose sight of the fact that public employees have a constitutional right to bargain collectively. Art. I, § 6, Fla. Const. (“The right of employees, by and through a labor organization, to bargain collectively shall not be denied or abridged.”). The Florida Supreme Court has made it clear that “ ‘with the exception of the right to strike, public employees have the same rights of collective bargaining as are granted private employees by Section 6 [of Article 1 of the Florida Constitution].’ ” City of Tallahassee v. Pub. Emps. Relations Comm’n, 410 So.2d 487, 490 (Fla.1981) (quoting Dade Cnty. Classroom Teachers’ Ass’n, Inc. v. Ryan, 225 So.2d 903, 905 (Fla.1969)). See also Chiles v. State Emps. Attorneys Guild, 734 So.2d 1030, 1036 (Fla.1999) (Article 1, section 6 of the Florida Constitution “expressly applies to ‘employees’ without limitation, except that public employees do not have the right to strike.”).

Implementing this constitutional right, the Public Employees Relations Act, Chapter 447, Part II (PERA), provides:

The public policy of this state, and the purpose of this part, is to provide statutory implementation of s. 6, Art. 1 of the State Constitution, with respect to public employees ... This state’s public policy is best effectuated by ... [Requiring the state, local governments, and other political subdivisions to negotiate with bargaining agents duly certified to represent public employees.

*1074§ 447.201, Fla. Stat. (2008). Section 447.309(1), Florida Statutes (2008), requires a public employer to bargain collectively the wages, hours, and other terms and conditions of employment for employees in each certified bargaining unit.2

Job-related benefits, although not catalogued in an existing bargaining agreement, may nevertheless constitute terms and conditions of employment which are not subject to change by the employer unilaterally. See Palowitch v. Orange Cnty. Sch. Bd., 3 F.P.E.R. 280 at 282 (1977), approved 367 So.2d 730 (Fla. 4th DCA 1979). “It is settled law that a public employer’s unilateral alteration of the status quo of a mandatory subject of bargaining, i.e., wages, hours, and terms and conditions of employment of its employees, is a per se violation of Section 447.501(1)(a) and (c), Florida Statutes, absent a clear and unmistakable waiver, legislative body action taken after impasse, or extraordinary circumstances requiring immediate action.” Miami Beach Fraternal Order of Police. William Nichols Lodge No. 8 v. City of Miami Beach, 36 F.P.E.R. 127 at 275-76 (2010). The status quo depends both on the provisions of collective bargaining agreements and on the content of established past practices. At issue here is the City’s allegedly established past practice of defraying a percentage of municipal employees’ health insurance premiums upon retirement.

Like private employees,3 public employees have the right to bargain for changes to established past practices, even though they are not mentioned in collective bargaining agreements. See Sch. Bd. of Orange Cnty. v. Palowitch, 367 So.2d 730, 731 (Fla. 4th DCA 1979) (school board’s unilateral increase of length of work year, as established by past practice, was a per se violation). In Palowitch, the Fourth District adopted PERC’s order, which explained:

The same policy considerations underlying the prohibition of unilateral changes during negotiations are equally applicable to unilateral changes in subjects not covered by an existing agreement. Terns and conditions not discussed by the parties in negotiations nevertheless continue to be terms and conditions of employment and, by virtue of Section ¼7.309(1), an employer must negotiate with the certified bargaining agent prior to changing them. The obligation to bargain imposed by Section 447.309(1), extends to all terms and conditions of employment. To conclude that terms and conditions of employment upon which the parties fail to reach agreement lose their status as such and somehow become management *1075prerogatives leads to an absurd and fruitless result.

Adoption of the School Board’s argument would require a bargaining agent for employees to bargain and reach agreement on every conceivable item falling within the scope of “wages, hours, and terms and conditions of employment” or suffer immediate waiver upon the execution of an agreement.

Palowitch, 367 So.2d at 731-32 (emphasis supplied). Public employees’ right to bargain for changes to established past practices includes the right to bargain for changes to the employer’s contribution to current employees’ health care premiums upon retirement4 where the union contract is silent on this issue. See Hillsborough Cnty. Police Benevolent Ass’ n, Inc. v. City of New Port Richey, 12 F.P.E.R. 17040 at 61 (1985).

In City of New Port Richey, PERC held that the city had committed an unfair labor practice, in violation of §§ 447.501(l)(a) and (c), by amending its ordinance to reduce its required contribution to the retirement fund where the city’s contribution had been established by ordinance for four years and the union contract was silent on the matter. PERC explained that:

an employer’s unilateral alteration of terms and conditions of employment established by past practice will give rise to an unfair labor practice when it is established that the past practice had been unequivocal, had existed substantially unvaried for a significant period of time prior to the change, and could reasonably have been expected by the employees to have continued unchanged.

Id. PERC went on to say that “... the City’s rate and ratio of contribution to the pension fund had, through past practice [four years], ripened into an extra-contractual term and condition of employment which was unilaterally changed by the City.” Id. Surprisingly, PERC made no mention of its decision in City of New Port Richey in the order under review.

The formula under which the City made its contribution toward retirees’ health insurance premiums in the present case remained in effect from 1995 to 2008. “To constitute an established practice, it must be demonstrated that the practice was unequivocal, that it existed substantially unvaried for a significant period of time, and that the bargaining unit employees could reasonably have expected the practice to continue unchanged.” Clay Educ. Staff Prof l Ass’n v. Sch. Dist. of Clay Cnty., 34 F.P.E.R. 139 at 275 (2008) (citing Hillsborough Cnty. Police Benevolent Ass’n, Inc. v. City of Tampa, 15 F.P.E.R. 20028 (1988); Manatee Educ. Ass’n v. Manatee Cnty. Sch. Bd., 7 F.P.E.R. 12017 (1980)). The hearing officer found as a fact that appellants’ members reasonably expected the City’s contri*1076butions to the health insurance premiums that they would pay when they retired would continue, based in no small part on the length of time that the formula for the City’s contributions had already remained in place.

This finding of fact has ample support in the evidence, and should not have been overturned. See Green v. Fla. Dep’t of Bus. & Prof'l Regulation, 49 So.3d 315, 318-19 (Fla. 1st DCA 2010) (determining that ALJ’s determinations that an appraisal report was not misleading or insufficient were factual findings, “susceptible to ordinary methods of proof and, thus, the Board was not permitted to reject these findings unless they were not supported by competent substantial evidence”); City of Winter Springs, 885 So.2d at 497 (“Agencies are bound to honor a hearing officer’s findings of fact unless they are not supported by competent, substantial evidence.” (citing Belleau, 695 So.2d at 1307)). PERC has in the past found that practices lasting much shorter periods of time gave public employees sufficient reason to expect the practice to persist. For example, in City of New Port Richey, PERC found that the city committed an unfair labor practice when it unilaterally reduced its contribution to a pension plan. PERC found that New Port Richey’s employees could reasonably have expected the practice to remain unchanged where the city’s rate of contribution to the plan had lasted from 1981 to 1985, or, as PERC said, “remained substantially unvaried for an extended period of time.” 12 F.P.E.R. 17040 at 61. There the contribution rates and ratios remained unchanged for a period of four years, while the period here lasted thirteen years.

PERC has, indeed, held that such a past practice can develop over the course of only two years. See Cent. Fla. Prof'l Firefighters, Local 2057 v. Bd. of Cnty. Comm’rs of Orange Cnty., 9 F.P.E.R. 14372 at 775-76 (1983) (employees had reasonable expectation that June 1, 1981 to May 2, 1983 practice allowing firefighters to leave the station to purchase food and eat at restaurants would continue). An agency’s interpretation of a statute it is charged with administering is normally entitled to judicial deference. But

“[a]n agency’s construction of a statute is not entitled to deference where the agency has erroneously interpreted a provision of law.” PERC must itself comply with statutes it administers that are intended to implement state constitutional provisions forbidding the abridgment of public employees’ collective bargaining rights. See Art. I, § 6, Fla. Const.

United Faculty of Fla. v. Pub. Emps. Relations Comm’n, 898 So.2d 96, 100-01 (Fla. 1st DCA 2005) (quoting City of Safety Harbor v. Commc’ns Workers of Am., 715 So.2d 265, 266 (Fla. 1st DCA 1998)) (reversing PERCs dismissal of unfair labor practice charges). Deference is particularly inappropriate where, as here, PERC has suddenly changed its interpretation of a statute with little or no explanation. See Fla. Cities Water Co. v. State, 705 So.2d 620, 625-26 (Fla. 1st DCA 1998); cf. Smith v. Crawford, 645 So.2d 513, 521 (Fla. 1st DCA 1994) (“Deference to an agency’s interpretation is even more compelling where an agency’s interpretation, as here, is consistent with its prior published opinions.”). The unequivocal past practice in the present case remained in place over the course of thirteen years, and was clearly well established, as the hearing officer found.

An employer’s unratified reservation of rights, whether in a retirement plan or in other documents not expressly incorporated into the collective bargaining agreement, does not abridge employees’ right to bargain collectively. See S. Nude- *1077 ar Operating Co. v. NLRB, 524 F.3d 1350 (D.C.Cir.2008); Midwest Power Systems, Inc., 335 NLRB 237, 238 (2001). Where the employer is a city, a municipal ordinance cannot abridge public employees’ constitutional and statutory rights5 to bargain collectively over past practices. See City of New Port Richey, 12 F.P.E.R. 17040 at 61. As explained by the Florida Supreme Court:

Municipal ordinances are inferior in stature and subordinate to the laws of the state. Accordingly, an ordinance must not conflict with any controlling provision of a state statute, and if any doubt exists as to the extent of a power attempted to be exercised which may affect the operation of a state statute, the doubt is to be resolved against the ordinance and in favor of the statute. A municipality cannot forbid what the legislature has expressly licensed, authorized or required, nor may it authorize what the legislature has expressly forbidden. In order for a municipal ordinance to prohibit that which is allowed by the general laws of the state there must be an express legislative grant by the state to the municipality authorizing such prohibition.

Rinzler v. Carson, 262 So.2d 661, 668 (Fla. 1972) (citations omitted). An employer’s published claim that it has retained the right to change a past practice without bargaining, does not give the employer the legal right to make the unbargained for change. See Pasco Cnty. Prof'l Firefighters, Local 4420, IAFF v. Pasco Cnty. Bd. *1078 of Cnty. Comm’rs, 33 F.P.E.R. 225 (2007) (holding annual wage increase following a wage study was an established past practice subject to collective bargaining despite the county’s inherent discretion not to follow wage study recommendations).6

The key is the parties’ reasonable expectation that a past practice will continue. See Seminole Cnty. Prof'l Firefighters, Local 3251 v. Seminole Cnty., 31 F.P.E.R. 197 at 457-58 (2005) (finding employees had a reasonable expectation that the practice of providing take-home vehicles would continue despite the County’s generally unknown and amorphous policy that allowed County to eliminate take-home vehicles upon an annual review); Daytona Beach Fire/Rescue, Local 1162 v. City of Daytona Beach, 19 F.P.E.R. 24068 at 138—39 (1993), aff'd., 630 So.2d 194 (Fla. 5th DCA 1993) (holding an annual wage increase was a past practice despite City’s discretion); Fla. Nurses Ass’n v. Pub. Health Trust-Metro. Dade Cnty., 14 F.P.E.R. 19312 at 700-06 (1988) (finding employees whose collective bargaining agreement did not contain express provision regarding employer’s contribution to employee health insurance premium had a reasonable expectation that employer’s nine-year practice of subsidizing the cost of certain HMO family coverage would continue, notwithstanding this statement in the employer’s insurance booklet: “You ... must pay the cost of your family’s coverage”). The past practice in the present case was substantially unvaried for more than a decade. The hearing officer understandably found that the parties expected it to continue. PERC erred in overturning the hearing officer’s recommendation to treat the City’s unilateral change of this established past practice as an unfair labor practice.

Reversed and remanded.

THOMAS, J., concurs; DAVIS, J., Dissents With Opinion.

DAVIS, J.

dissenting.

I respectfully dissent and would affirm PERC’s order. In reversing, the majority primarily focuses on the length of time that the City of Gainesville used the 1995 formula in calculating its contribution toward retiree health insurance premiums. However, to constitute an established past practice, it must not only be shown that a practice has existed substantially unvaried for a significant period of time, it must also be shown that the practice was unequivocal and that the bargaining unit employees could reasonably have expected the practice to remain unchanged. United Faculty of Fla. v. Univ. of Cent. Fla. Bd. of Trs., 30 F.P.E.R. ¶ 229 (2004). This case turns on whether the employees had a reasonable expectation that the 1995 formula would remain unchanged. In my opinion, PERC was correct in concluding that they did not. Although the employees may have believed that the City’s contribution amount would remain unchanged, whether a practice has created a reasonable expectation must be analyzed on an objective, rather than a subjective, basis. See Daytona Beach Fire/Rescue, Local 1162 v. *1079 City of Daytona Beach, 19 F.P.E.R. ¶ 24068 (1993).

As PERC noted, the City has, on multiple occasions throughout the years, warned all of its employees of its reservation of rights with respect to its contribution toward retiree health care premiums. For instance, in the 1995 ordinance, wherein the City adopted its contribution formula, the City set forth:

WHEREAS, the City Commission ... has in the past chosen to pay some of the premium costs for continued health insurance coverage for retirees and/or their dependents, the percent or amount of which payment for either the retiree or dependent coverage has varied over the years and may continue to do so in the future....

The same or similar language was included in subsequent ordinances, as well as in memoranda, employee health care handbooks, and policy statements. This express reservation of rights distinguishes this case from the many PERC decisions cited by the majority. Had this case dealt only with a thirteen-year practice, those decisions would support reversal. However, in this case, the employees were continuously notified that the City could alter its contribution at any time, including in 1995, the point at which the unions argue that the status quo or past practice began. As PERC concluded, the employees could not reasonably expect that the City’s 1995 contribution formula would remain unchanged.

Accordingly, I would affirm.