Biggest changePercentage of Total Net Revenues ($ in thousands) Years Ended December 31, 2022 2021 2020 Revenues: Professional employer services $ 937,363 88.9 % $ 843,815 88.3 % $ 777,430 88.3 % Staffing services 116,963 11.1 111,351 11.7 $ 103,394 11.7 Total revenues 1,054,326 100.0 955,166 100.0 880,824 100.0 Cost of revenues: Direct payroll costs 87,944 8.3 83,821 8.8 78,380 8.9 Payroll taxes and benefits 522,392 49.5 469,888 49.2 418,793 47.5 Workers’ compensation 209,145 19.8 196,949 20.6 200,744 22.8 Total cost of revenues 819,481 77.7 750,658 78.6 697,917 79.2 Gross margin 234,845 22.3 204,508 21.4 182,907 20.8 Selling, general and administrative expenses 169,642 16.1 155,259 16.3 141,916 16.1 Depreciation and amortization 6,228 0.6 5,326 0.6 4,844 0.5 Income from operations 58,975 5.6 43,923 4.6 36,147 4.1 Other income, net 6,328 0.6 6,738 0.7 6,449 0.7 Income before income taxes 65,303 6.2 50,661 5.3 42,596 4.8 Provision for income taxes 18,035 1.7 12,582 1.3 8,831 1.0 Net income $ 47,268 4.5 % $ 38,079 4.0 % $ 33,765 3.8 % 26 We report PEO revenues net of direct payroll costs because we are not the primary obligor for wage payments to our clients’ employees.
Biggest changePercentage of Total Net Revenues ($ in thousands) Years Ended December 31, 2023 2022 2021 Revenues: Professional employer services $ 982,268 91.9 % $ 937,363 88.9 % $ 843,815 88.3 % Staffing services 87,039 8.1 116,963 11.1 111,351 11.7 Total revenues 1,069,307 100.0 1,054,326 100.0 955,166 100.0 Cost of revenues: Direct payroll costs 65,042 6.1 87,944 8.3 83,821 8.8 Payroll taxes and benefits 555,758 52.0 522,392 49.5 469,888 49.2 Workers’ compensation 205,975 19.2 209,145 19.8 196,949 20.6 Total cost of revenues 826,775 77.3 819,481 77.7 750,658 78.6 Gross margin 242,532 22.7 234,845 22.3 204,508 21.4 Selling, general and administrative expenses 174,772 16.3 169,642 16.1 155,259 16.3 Depreciation and amortization 7,110 0.7 6,228 0.6 5,326 0.6 Income from operations 60,650 5.7 58,975 5.6 43,923 4.6 Other income, net 8,338 0.8 6,328 0.6 6,738 0.7 Income before income taxes 68,988 6.5 65,303 6.2 50,661 5.3 Provision for income taxes 18,376 1.7 18,035 1.7 12,582 1.3 Net income $ 50,612 4.8 % $ 47,268 4.5 % $ 38,079 4.0 % 28 We report PEO revenues net of direct payroll costs because we are not the primary obligor for wage payments to our clients’ employees.
A relative increase in PEO services revenue will result in a higher gross margin as a percentage of revenue. Improvement in gross margin percentage occurs because incremental client services revenue dollars are reported as revenue net of all related direct payroll and safety incentive costs. We refer to employees of our PEO clients as worksite employees (“WSEs”).
Generally, a relative increase in PEO services revenue will result in a higher gross margin as a percentage of revenue. Improvement in gross margin percentage occurs because incremental client services revenue dollars are reported as revenue net of all related direct payroll and safety incentive costs. We refer to employees of our PEO clients as worksite employees (“WSEs”).
Property, equipment, software and internally developed software costs are depreciated using the straight-line method over their estimated useful lives, which range from 3 to 39 years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or estimated useful life.
Property, equipment, software and 25 internally developed software costs are depreciated using the straight-line method over their estimated useful lives, which range from 3 to 39 years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or estimated useful life.
Corporate-level operating expenses consist primarily of executive and office staff payroll and personnel related costs, professional and legal fees, travel, occupancy costs, information systems costs, and executive and corporate staff incentive compensation. 23 Depreciation and amortization represent depreciation of property and equipment, leasehold improvements, software and internally developed software costs.
Corporate-level operating expenses consist primarily of executive and office staff payroll and personnel related costs, professional and legal fees, travel, occupancy costs, information systems costs, and executive and corporate staff incentive compensation. Depreciation and amortization represent depreciation of property and equipment, leasehold improvements, software and internally developed software costs.
Our cost of revenues for staffing services includes direct payroll costs, employer payroll-related taxes, employee benefits, and workers’ compensation costs. Direct payroll costs represent the gross payroll earned by staffing services employees based on salary or hourly wages.
Our cost of revenues for staffing services includes direct payroll costs, employer payroll-related taxes, and workers’ compensation costs. Direct payroll costs represent the gross payroll earned by staffing services employees based on salary or hourly wages.
Such factors with respect to the Company include: our ability to retain current clients and attract new clients; the effects of governmental orders, laws or regulations imposing requirements related to the COVID-19 pandemic; difficulties associated with integrating clients into our operations; economic trends in our service areas; the potential for material deviations from expected future workers’ compensation claims experience; changes in the workers’ compensation regulatory environment in our primary markets; security breaches or failures in the Company’s information technology systems; collectability of accounts receivable; changes in effective payroll tax rates and federal and state income tax rates; the carrying values of deferred income tax assets and goodwill (which may be affected by our future operating results); the effects of inflation on our operating expenses and those of our clients; the impact of and potential changes to the Patient Protection and Affordable Care Act, escalating medical costs, and other health care legislative initiatives on our business; the effect of conditions in the global capital markets on our investment portfolio; and the availability of capital, borrowing capacity on our revolving credit facility, or letters of credit necessary to meet state-mandated surety deposit requirements for maintaining our status as a qualified self-insured employer for workers' compensation coverage or our insured program.
Such factors with respect to the Company include: our ability to retain current clients and attract new clients; difficulties associated with integrating clients into our operations; economic trends in our service areas; the potential for material deviations from expected future workers’ compensation claims experience; changes in the workers’ compensation regulatory environment in our primary markets; security breaches or failures in the Company’s information technology systems; collectability of accounts receivable; changes in executive management; changes in effective payroll tax rates and federal and state income tax rates; the carrying values of deferred income tax assets and goodwill (which may be affected by our future operating results); the effects of inflation on our operating expenses and those of our clients; the impact of and potential changes to the Patient Protection and Affordable Care Act, escalating medical costs, and other health care legislative initiatives on our business; the effect of conditions in the global capital markets on our investment portfolio; and the availability of capital, borrowing capacity on our revolving credit facility, or letters of credit necessary to meet state-mandated surety deposit requirements for maintaining our status as a qualified self-insured employer for workers' compensation coverage or our insured program.
Consequently, any weakness in economic conditions, changes in the regulatory or insurance environment, or natural disasters or other major events in California could have a material adverse effect on our financial results. Our cost of revenues for PEO services includes employer payroll-related taxes and workers' compensation costs.
Consequently, weakness in economic conditions, changes in the regulatory or insurance environment, or natural disasters or other major disruptive events in California could have a material adverse effect on our financial results. Our cost of revenues for PEO services includes employer payroll-related taxes, workers’ compensation costs and employee benefits costs.
A discussion of our financial condition and results of operations for 2021 compared to 2020 can be found in Part II, Item 7.
A discussion of our financial condition and results of operations for 2022 compared to 2021 can be found in Part II, Item 7.
We therefore present for purposes of analysis gross billings and wage information for the years ended December 31, 2022, 2021 and 2020.
We therefore present for purposes of analysis gross billings and wage information for the years ended December 31, 2023, 2022 and 2021.
Management's Discussion and Analysis in our Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 7, 2022. 28 Fluctuations in Quarterly Operating Results We have historically experienced significant fluctuations in our quarterly operating results, including losses or minimal income in the first quarter of each year, and expect such fluctuations to continue in the future.
Management's Discussion and Analysis in our Annual Report on Form 10-K for the year ended December 31, 2022, filed with the SEC on March 6, 2023. 30 Fluctuations in Quarterly Operating Results We have historically experienced significant fluctuations in our quarterly operating results, including losses or minimal income in the first quarter of each year, and expect such fluctuations to continue in the future.
Our business is concentrated in California, and we expect to continue to derive a majority of our revenues from this market in the future. Revenues generated in our California operations accounted for 73% of our total revenues in 2022, 73% in 2021 and 75% in 2020.
Our business is concentrated in California, and we expect to continue to derive a majority of our revenues from this market in the future. Revenues generated in our California operations accounted for 72% of our total revenues in 2023, 73% in 2022 and 73% in 2021.
Percentage of Gross Billings Year Ended December 31, 2022 2021 2020 PEO and staffing wages 86.9 % 86.7 % 86.1 % Payroll taxes and benefits 7.0 % 7.2 % 7.1 % Non-GAAP gross workers' compensation 2.9 % 3.0 % 3.8 % Gross margin 3.2 % 3.1 % 3.1 % The presentation of revenue on a net basis and the relative contributions of staffing and PEO services revenue can create volatility in our gross margin as a percentage of revenue.
Percentage of Gross Billings Year Ended December 31, 2023 2022 2021 PEO and staffing wages 87.0 % 86.9 % 86.7 % Payroll taxes and benefits 7.2 % 7.0 % 7.2 % Workers' compensation 2.7 % 2.9 % 3.0 % Gross margin 3.1 % 3.2 % 3.1 % The presentation of revenue on a net basis and the relative contributions of staffing and PEO services revenue can create volatility in our gross margin as a percentage of revenue.
The Company is required to maintain minimum collateral levels for certain policies issued under the insured program, which is held in a trust account (the “trust account”). The balance in the trust account was $188.2 million and $273.6 million at December 31, 2022 and December 31, 2021, respectively.
The Company is required to maintain minimum collateral levels for certain policies issued under the insured program, which is held in a trust account (the “trust account”). The balance in the trust account was $210.9 million and $188.2 million at December 31, 2023 and December 31, 2022, respectively.
The increase in PEO services revenues was primarily attributable to an increase in average number of WSEs as well as an increase in average billing per WSE. Gross margin for 2022 totaled $234.8 million or 22.3% of revenue compared to $204.5 million or 21.4% of revenue for 2021.
The increase in PEO services revenues was primarily attributable to an increase in average number of WSEs as well as an increase in average billing per WSE. Gross margin for 2023 totaled $242.5 million or 22.7% of revenue compared to $234.8 million or 22.3% of revenue for 2022.
The increase in gross margin as a percentage of revenues is primarily a result of the factors discussed within the separate components of gross margin below. Direct payroll costs for 2022 totaled $87.9 million or 8.3% of revenue compared to $83.8 million or 8.8% of revenue for 2021.
The increase in gross margin as a percentage of revenues is primarily a result of the factors discussed within the separate components of gross margin below. Direct payroll costs for 2023 totaled $65.0 million or 6.1% of revenue compared to $87.9 million or 8.3% of revenue for 2022.
These forward-looking statements include, among others, discussion of economic conditions in our market areas and their effect on revenue levels, the lingering effects of the COVID-19 pandemic on our business operations, the competitiveness of our service offerings, the availability of certain fully insured medical and other health and welfare benefits to qualifying worksite employees beginning in 2023, our ability to attract and retain clients and to achieve revenue growth, the effect of changes in our mix of services on gross margin, the effect of tight labor market conditions, the adequacy of our workers' compensation reserves, the effect of changes in estimates of our future claims liabilities on our workers’ compensation reserves, including the effect of changes in our reserving practices and claims management process on our actuarial estimates, expected levels of required surety deposits and letters of credit, our ability to generate sufficient taxable income in the future to utilize our deferred tax assets, the effect of our formation and operation of two wholly owned licensed insurance subsidiaries, the risks of operation and cost of our insured program, the financial viability of our excess insurance carriers, the effectiveness of our management information systems, our relationship with our primary bank lender and the availability of financing and working capital to meet our funding requirements, litigation costs, the effect of changes in the interest rate environment on the value of our investment securities, the adequacy of our allowance for doubtful accounts, and the potential for and effect of acquisitions. 25 All our forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause the actual results, performance or achievements of the Company or industry to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements.
These forward-looking statements include, among others, discussion of economic conditions in our market areas and their effect on revenue levels, the lingering effects of the COVID-19 pandemic on our business operations, the competitiveness of our service offerings, the availability of certain fully insured medical and other health and welfare benefits to qualifying worksite employees, our ability to attract and retain clients and to achieve revenue growth, the effect of changes in our mix of services on gross margin, labor market conditions, the adequacy of our workers' compensation reserves, the effect of changes in estimates of our future claims liabilities on our workers’ compensation reserves, including the effect of changes in our reserving practices and claims management process on our actuarial estimates, expected levels of required surety deposits and letters of credit, our ability to generate sufficient taxable income in the future to utilize our deferred tax assets, the effect of our formation and operation of two wholly owned licensed insurance subsidiaries, the risks of operation and cost of our insured program, the financial viability of our excess insurance carriers, the effectiveness of our management information systems, our relationship with our primary bank lender and the availability of financing and working capital to meet our funding requirements, litigation costs, the effect of changes in the interest rate environment on the value of our investment securities, the adequacy of our allowance for doubtful accounts, and the potential for and effect of acquisitions.
See “Note 5 - Revolving Credit Facility and Long-Term Debt” to the consolidated financial statements included in Item 8 of Part II of this report for information regarding the Company’s credit agreement with Wells Fargo Bank, N.A. 29 Contractual Obligations The Company's contractual obligations as of December 31, 2022 are summarized below: As of December 31, 2022 Payments Due by Period (in thousands) Less than 1 - 3 4 - 5 After Total 1 Year Years Years 5 Years Operating leases (1) $ 24,624 $ 7,870 $ 10,303 $ 5,221 $ 1,230 Total contractual obligations $ 24,624 $ 7,870 $ 10,303 $ 5,221 $ 1,230 (1) As of December 31, 2022, the Company has additional operating leases that have not yet commenced of $1.7 million and remaining balances on short-term operating leases of $37,301.
See “Note 5 - Revolving Credit Facility and Long-Term Debt” to the consolidated financial statements included in Item 8 of Part II of this report for information regarding the Company’s credit agreement with Wells Fargo Bank, N.A. 31 Contractual Obligations The Company's contractual obligations as of December 31, 2023 are summarized below: As of December 31, 2023 Payments Due by Period (in thousands) Less than 1 - 3 4 - 5 After Total 1 Year Years Years 5 Years Operating leases (1) $ 24,311 $ 7,571 $ 10,171 $ 5,767 $ 802 Total contractual obligations $ 24,311 $ 7,571 $ 10,171 $ 5,767 $ 802 (1) As of December 31, 2023, the Company has additional operating leases that have not yet commenced of $1.0 million and remaining balances on short-term operating leases of $60,332.
The decrease in direct payroll costs as a percentage of revenues was primarily due to a decrease in staffing services within the mix of our customer base in 2022 as compared to 2021. Payroll taxes and benefits for 2022 totaled $522.4 million or 49.5% of revenue compared to $469.9 million or 49.2% of revenue for 2021.
The decrease in direct payroll costs as a percentage of revenues was primarily due to a decrease in staffing services within the mix of our customer base in 2023 as compared to 2022. Payroll taxes and benefits for 2023 totaled $555.8 million or 52.0% of revenue compared to $522.4 million or 49.5% of revenue for 2022.
Net cash provided by investing activities totaled $61.2 million in 2022, compared to net cash used of $112.9 million for the comparable period of 2021.
Net cash used in investing activities totaled $55.2 million in 2023, compared to net cash provided of $61.2 million for the comparable period of 2022.
Significant structural changes to the available data can materially impact the reserve estimation process. To the extent a material change affecting the ultimate claim liability becomes known, such change is quantified to the extent possible through an analysis of internal company data and, if available and when appropriate, external data.
To the extent a material change affecting the ultimate claim liability becomes known, 26 such change is quantified to the extent possible through an analysis of internal company data and, if available and when appropriate, external data.
Workers' compensation costs consist primarily of the costs associated with our workers' compensation program, including premiums for the insured program, claims reserves for the self-insured program, claims administration fees, legal fees, medical cost containment (“MCC”) expense, state administrative agency fees, third-party broker commissions, risk manager payroll, premiums for excess insurance, and costs associated with operating our two wholly owned insurance companies, AICE and Ecole.
Workers’ compensation costs consist primarily of premiums paid to third-party insurers, claims reserves, claims administration fees, legal fees, medical cost containment (“MCC”) expense, state administrative agency fees, third-party broker commissions, and risk manager payroll, as well as costs associated with operating our two wholly owned insurance companies, Associated Insurance Company for Excess (“AICE”) and Ecole Insurance Company (“Ecole”).
Net cash provided by operating activities in 2022 amounted to $27.8 million, compared to net cash used of $15.5 million for the comparable period of 2021.
Net cash provided by operating activities in 2023 amounted to $67.2 million, compared to net cash provided of $27.8 million for the comparable period of 2022.
Year Ended December 31, 2022 % Change 2021 % Change 2020 Average WSEs 122,001 8.0 % 112,928 4.3 % 108,249 Ending WSEs 122,306 5.3 % 116,154 6.3 % 109,292 27 Years Ended December 31, 2022 and 2021 Net income for 2022 was $47.3 million compared to net income of $38.1 million for 2021.
Year Ended December 31, 2023 % Change 2022 % Change 2021 Average WSEs 124,306 1.9 % 122,001 8.0 % 112,928 Ending WSEs 126,446 3.4 % 122,306 5.3 % 116,154 29 Years Ended December 31, 2023 and 2022 Net income for 2023 was $50.6 million compared to net income of $47.3 million for 2022.
Diluted net income per share for 2022 was $6.54 compared to diluted income per share of $5.00 for 2021.
Diluted net income per share for 2023 was $7.39 compared to diluted income per share of $6.54 for 2022.
Due to the inherent uncertainty underlying loss reserve estimates, the expenses incurred through final resolution of our liability for our workers’ compensation claims will likely vary from the related loss reserves at the reporting date.
Due to the inherent uncertainty underlying loss reserve estimates, the expenses incurred through final resolution of our liability for our workers’ compensation claims will likely vary from the related loss reserves at the reporting date. Therefore, as specific claims are paid out in the future, actual paid losses may be materially different from our current loss reserves.
Results of Operations The following table sets forth the percentages of total revenues represented by selected items in the Company's consolidated statements of operations for the years ended December 31, 2022, 2021 and 2020, included in Item 8 of Part II of this report.
We disclaim any obligation to publicly announce any revisions to any of the forward-looking statements contained herein to reflect future events or developments. 27 Results of Operations The following table sets forth the percentages of total revenues represented by selected items in the Company's consolidated statements of operations for the years ended December 31, 2023, 2022 and 2021, included in Item 8 of Part II of this report.
Liquidity and Capital Resources The Company's cash balance of $107.4 million, which includes cash, cash equivalents, and restricted cash, increased $28.7 million for the twelve months ended December 31, 2022, compared to a decrease of $155.2 million for the comparable period of 2021.
Liquidity and Capital Resources The Company's cash balance of $74.8 million, which includes cash, cash equivalents, and restricted cash, decreased $32.5 million for the twelve months ended December 31, 2023, compared to an increase of $28.7 million for the comparable period of 2022.
Net cash used in financing activities in 2022 was $60.2 million compared to net cash used of $26.9 million for the comparable period of 2021. In 2022, net cash used in financing activities primarily consisted of repurchases of common stock of $47.2 million, dividend payments of $8.5 million and the payoff of the outstanding mortgage loan balance of $3.5 million.
Net cash used in financing activities in 2023 was $44.6 million compared to net cash used of $60.2 million for the comparable period of 2022. In 2023, net cash used in financing activities primarily consisted of repurchases of common stock of $34.2 million and dividend payments of $8.1 million.
The increase in cash at December 31, 2022 as compared to December 31, 2021 was primarily due to proceeds from the sales and maturities of investments and restricted investments, net income, increased accrued payroll, payroll taxes and related benefits, and increased other accrued liabilities, partially offset by decreased workers' compensation claims liabilities, repurchase of common stock, and purchase of property, equipment and software.
The decrease in cash at December 31, 2023 as compared to December 31, 2022 was primarily due to the purchase of investments and restricted investments, decreased workers' compensation claim liabilities, and repurchases of common stock partially offset by increased premium payable, net income, and proceeds from the sale and maturities of investments and restricted investments.
Other income, net for 2022 totaled $6.3 million compared to other income of $6.7 million for 2021. The decrease was primarily attributable to a decrease in investment income in 2022. Our effective income tax rate for 2022 was 27.6% compared to 24.8% for 2021.
The increase of $5.2 million in SG&A expense was primarily attributable to increased employee-related costs. Other income, net for 2023 totaled $8.3 million compared to other income of $6.3 million for 2022. The increase was primarily attributable to an increase in investment income in 2023. Our effective income tax rate for 2023 was 26.6% compared to 27.6% for 2022.
In 2022, net cash provided by operating activities was primarily due to net income of $47.3 million, increased accrued payroll, payroll taxes and related benefits of $24.9 million and increased other accrued liabilities of $15.7 million, partially offset by decreased workers’ compensation claims liabilities of $64.2 million and increased trade accounts receivable of $8.1 million.
In 2023, net cash provided by operating activities was primarily due to increased premium payable of $54.2 million, net income of $50.6 million, and increased accrued payroll, payroll taxes and related benefits of $12.7 million, partially offset by decreased workers’ compensation claims liabilities of $51.2 million.
Revenue for 2022 totaled $1,054.3 million, an increase of $99.2 million or 10.4% over 2021, which reflects an increase in the Company’s PEO service revenue of $93.5 million or 11.1% and an increase in staffing services revenue of $5.6 million or 5.0%.
Revenue for 2023 totaled $1,069.3 million, an increase of $15.0 million or 1.4% over 2022, which reflects an increase in the Company’s PEO service revenue of $44.9 million or 4.8% and a decrease in staffing services revenue of $29.9 million or 25.6%.
Therefore, as specific claims are paid out in the future, actual paid losses may be materially different from our current loss reserves. 24 A basic premise in most actuarial analyses is that historical data and past patterns demonstrated in the incurred and paid historical data form a reasonable basis upon which to project future outcomes, absent a material change.
A basic premise in most actuarial analyses is that historical data and past patterns demonstrated in the incurred and paid historical data form a reasonable basis upon which to project future outcomes, absent a material change. Significant structural changes to the available data can materially impact the reserve estimation process.
Selling, general and administrative (“SG&A”) expenses for 2022 totaled $169.6 million or 16.1% of revenue compared to $155.3 million or 16.3% of revenue for 2021. The increase of $14.3 million in SG&A expense in 2022 was primarily attributable to increased employee related costs, as well as increased travel and marketing expenses due to more in-person meetings and events.
Selling, general and administrative (“SG&A”) expenses for 2023 totaled $174.8 million or 16.3% of revenue compared to $169.6 million or 16.1% of revenue for 2022. The increase as a percentage of revenue was primarily due to the decrease in staffing services within the mix of our customer base.
In 2022, net cash provided by investing activities consisted primarily of proceeds from sales and maturities of investments and restricted investments of $81.5 million, partially offset by purchase of property, equipment and software of $16.0 million, and purchase of restricted investments of $4.3 million.
In 2023, net cash used in investing activities consisted primarily of purchase of investments and restricted investments of $71.1 million and purchase of property, equipment and software of $11.8 million, partially offset by proceeds from the sale and maturity of investments and restricted investments of $27.6 million.
Additional risk factors affecting our business are discussed in Item 1A of Part I of this report. We disclaim any obligation to publicly announce any revisions to any of the forward-looking statements contained herein to reflect future events or developments.
Additional risk factors affecting our business are discussed in Item 1A of Part I of this report.
The increase in payroll taxes and benefits expense as a percentage of revenue was primarily due to the relative decrease in workers' compensation costs and an increase in federal payroll tax rates, partially offset by lower average state payroll tax rates in 2022.
The increase in payroll taxes and benefits expense as a percentage of revenue was primarily due to higher average payroll tax rates in 2023, in addition to PEO client benefit costs of $10.5 million related to the availability of employee benefits to our PEO clients beginning in 2023.
Workers’ compensation expense for 2022 totaled $209.1 million or 19.8% of revenue compared to $196.9 million or 20.6% of revenue for 2021. The decrease in workers’ compensation expense as a percentage of revenue was primarily due to favorable adjustments of $11.3 million related to prior period claims in 2022, compared to favorable adjustments of $9.2 million in 2021.
The decrease in workers’ compensation expense as a percentage of revenue was primarily due to lower workers' compensation costs in the current year as well as favorable prior year liability and premium adjustments of $14.9 million in 2023, compared to prior year liability and premium adjustments of $13.4 million in 2022.
Year Ended December 31, (in thousands) 2022 2021 2020 Gross billings $ 7,393,808 $ 6,569,986 $ 5,924,539 PEO and staffing wages 6,425,286 5,693,903 5,098,604 Because safety incentives represent consideration payable to PEO customers, safety incentive costs are netted against PEO revenue in our consolidated statements of operations.
Year Ended December 31, (in thousands) 2023 2022 2021 Gross billings $ 7,716,152 $ 7,393,808 $ 6,569,986 PEO and staffing wages 6,711,115 6,425,286 5,693,903 In monitoring and evaluating the performance of our operations, management also reviews the following ratios, which represent selected amounts as a percentage of gross billings.
Payroll taxes and employee benefits consist of the employer's portion of Social Security and Medicare taxes, federal and state unemployment taxes and staffing services employee reimbursements for materials, supplies and other expenses, which are paid by our customer.
Payroll taxes and benefits consist of the employer’s portion of Social Security and Medicare taxes, federal and state unemployment taxes, and employee benefit costs, which primarily comprises health insurance premiums paid to third-party insurers and underwriting and benefit consultant payroll.