Revenue grew 18% for the year and is on pace to recover to pre-pandemic levels two years faster than the previous recession.
Revenue was $622 million, an increase of 20%, compared to Q4 2020 and up 5% versus Q4 2019.
These factors produced adjusted EBITDA of $36 million, an increase of $14 million compared to Q4 2020 and an increase of $15 million compared to Q4 2019.
PeopleReady is our largest segment, representing 59% of total trailing 12-month revenue and 63% of total segment profit.
Year-over-year PeopleReady revenue was up 22% during the quarter.
Compared to the fourth quarter of 2019, we recovered 99% of our revenue, which is an improvement of 15 points from the recovery rate in the third quarter of this year.
Retail results were strong during the quarter, increasing 100% year-over-year led by a seasonal surge, combined with ongoing project work.
PeopleManagement is our second largest segment, representing 29% of total trailing 12-month revenue and 10% of total segment profit.
Even though PeopleManagement revenue exceeded the comparable 2019 period by 4%, revenue declined 1% in the fourth quarter.
Turning to our third segment, PeopleScout represents 12% of total trailing 12-month revenue and 27% of total segment profit.
Revenue momentum at PeopleScout continued during the fourth quarter, growing 96% year over year and surpassing the comparable 2019 period by 49%.
PeopleScout's strong results were driven by growth in existing client volumes of 71% year over year due to surging client demand and new customer wins.
Since rolling out the application to associates in 2017 and to our clients in 2018, associate adoption has grown to over 90%, and our JobStack client user count ended the quarter at 29,700, up 13% versus Q4 2020.
As a reminder, a heavy user has 50 or more touches on JobStack per month, whether it's entering an order, rating a worker, or approving time.
Overall, heavy client users account for 56% of PeopleReady US on-demand revenue compared to 35% in Q4 2020.
We've also seen continued growth in our digital fill rates, which have increased 3x since rollout to nearly 60%, with 964,000 shifts filled via the app during the quarter.
As a reminder, the service centers increase our accessibility as they operate 85 hours per week versus 60 hours for a typical branch.
Once the service center rollout is complete, we expect annual run-rate cost savings of $10 million to $15 million.
PeopleManagement secured annualized new business wins of $95 million this year, up more than 40% versus the three prior year comparable average, helping to offset recent supply chain challenges.
Our efforts are delivering results with annualized new wins of $39 million this year versus the three-year prior comparable average of $11 million.
Total revenue for Q4 2021 was $622 million, representing growth of 20% compared to Q4 2020 and growth of 5% compared to Q4 2019.
We posted net income of $20 million or $0.57 per share, an increase of $12 million compared to Q4 2020 and an increase of $11 million compared to Q4 2019.
We delivered adjusted EBITDA of $36 million, an increase of $14 million compared to Q4 2020 and an increase of $15 million compared to Q4 2019.
Adjusted EBITDA margin was up 160 basis points compared to Q4 2020 and up 230 basis points compared to Q4 2019, with growth in 2021, again, driven by revenue growth and gross margin expansion.
Gross margin for Q4 2021 of 26.8% was up 350 basis points.
Our staffing segments contributed 310 basis points of margin expansion, comprised of 110 basis points from lower workers' compensation costs mainly due to favorable development of prior-period reserves; 70 basis points from favorable bill/pay spreads; 70 basis points from increasing PeopleReady sales mix, which carries a higher margin than PeopleManagement; and 60 basis points from PeopleReady customer mix.
Higher PeopleScout sales mix contributed the remaining 40 basis points of expansion.
SG&A expense increased 33%, which was higher than our revenue growth of 20% due to the magnitude of the cost actions taken in Q4 last year.
As a reminder, in Q4 2020, our cost management actions produced a decline in SG&A of 22%, which outpaced the revenue decline of 12% for the quarter.
SG&A as percentage of revenue in Q4 2021 improved by 30 basis points in comparison with Q4 2019.
Our effective income tax rate was 21% in Q4, which was slightly higher than expected due to lower tax credits.
Turning to our segments, PeopleReady revenue increased 22%, while segment profit increased 69%, and segment margin was up 210 basis points.
Revenue in the retail sector increased 100% year over year, largely due to a seasonal surge from one client, which contributed about half of the retail sector growth, or 4 percentage points of growth for the PeopleReady business, which we do not expect will carry into the first quarter.
PeopleManagement revenue decreased 1%, while segment profit decreased 20%, with 60 basis points of margin contraction.
Same-site sales are being negatively impacted by supply chain disruptions, which created a drag of approximately 4 percentage points during the quarter.
PeopleScout revenue increased 96%, with segment profit up $7 million and over 300 basis points of margin expansion.
During the quarter, same customer demand surged 71% year over year.
Of the increase, approximately 15 percentage points was related to clients catching up to pre-pandemic hiring levels.
We finished the quarter with $50 million in cash and no outstanding debt.
During the quarter, we repurchased $17 million of common stock and $13 million was purchased during the first quarter of this year.
The board of directors also authorized an additional $100 million in share repurchases, which we intend to complete over the next three years.
In the first quarter, we expect approximately $3 million in operating costs as we prepare to implement this system at the end of this year and roughly $10 million for the full year.
We expect $2 million in accelerated depreciation for full year 2022.

Summary:
Revenue was $622 million, an increase of 20%, compared to Q4 2020 and up 5% versus Q4 2019.
Total revenue for Q4 2021 was $622 million, representing growth of 20% compared to Q4 2020 and growth of 5% compared to Q4 2019.
We posted net income of $20 million or $0.57 per share, an increase of $12 million compared to Q4 2020 and an increase of $11 million compared to Q4 2019.