We achieved $0.89 in adjusted earnings per share and $60 million of adjusted EBITDA above the midpoint of our forecasted ranges and driven by the quick rebound to double-digit worksite employee growth from the pandemic lows experienced in the prior year.
As per our growth metric, the average number of paid worksite employees increased by 11% over Q3 of 2020, above the high end of our forecasted range of 9.5% to 10.5%.
This was a sequential increase of 6% over Q2 of 2021.
The accelerated worksite employee growth was driven by net gains from hiring in our client base exceeding our targets, worksite employees paid from new sales and third quarter client retention of 99%.
Now along with worksite employee growth, our revenue per worksite employee, which reflected a 4% increase in pricing and the non-recurrence of the 2020 FICA deferral also exceeded our expectations.
Q3 cash operating expenses increased 9% over the prior year, slightly below forecasted levels.
During the quarter, we repurchased 106,000 shares of stock at a cost of $11 million, bringing our year-to-date repurchases up to 544,000 shares at a cost of $50 million.
Additionally over the course of the first three quarters of this year, we have paid out $50 million in cash dividends and invested $24 million in capital expenditures.
We ended Q3 with $228 million of adjusted cash and $370 million of debt.
Our recent growth acceleration to 11% in paid worksite employees over last year was caused by our three primary drivers hitting on all cylinders, namely new client sales, client retention and net gain and employment within our client base.
In addition to the strong net gain in employment in the client base, we saw an 18% improvement in paid worksite employees from sales of new accounts and a 16% improvement in fewer employees lost from client attrition over the same period last year.
Booked sales of new accounts in the third quarter was excellent with approximately the same number of business performance advisors as last year selling 20% more clients and 30% more worksite employees than in the same period in 2020.
A simple way to understand the impact of the maturity of the BPA team is to look at the number and percentage of trained BPAs with less than 18 months experience, 18 to 36 months experience, and those with greater than 36 months experience.
Generally, the group in the middle with 18 to 36 months experience has approximately the average sales efficiency.
Now, we've been growing the number of trained BPAs at an average rate of approximately 13% per year from 2016 through 2020, resulting in an increase in the total trained BPAs by 80%.
This significant increase in the number of BPAs with greater than 36 months experience and the corresponding increase in overall sales efficiency, creates a new opportunity for us.
In the past, we focused on growing at higher rates by continuing to grow the BPA team over 10% each year.
The departure of that 6800 employee client in January is somewhat masking the excellent client retention for this year.
We are forecasting Q4 average paid worksite employee growth of 11% to 12% over Q4 of 2020, a slight acceleration from the double-digit growth rate achieved in Q3.
When combined with our outperformance in the three previous quarters, we are now forecasting full year worksite employee growth of about 7% above our previous guidance of 5.5% to 6.5%.
We are forecasting a 19% to 48% increase in Q4 adjusted EBITDA to a range of $45 million to $56 million and a 24% to 65% increase in adjusted earnings per share to a range of $0.61 to $0.81.
And when combining our Q4 earnings outlook with our outperformance over the previous three quarters, we now expect full year 2021 adjusted earnings per share to be in a range of $4.25 to $4.46 and adjusted EBITDA of $271 million to $282 million.

Summary:
We achieved $0.89 in adjusted earnings per share and $60 million of adjusted EBITDA above the midpoint of our forecasted ranges and driven by the quick rebound to double-digit worksite employee growth from the pandemic lows experienced in the prior year.
As per our growth metric, the average number of paid worksite employees increased by 11% over Q3 of 2020, above the high end of our forecasted range of 9.5% to 10.5%.
Booked sales of new accounts in the third quarter was excellent with approximately the same number of business performance advisors as last year selling 20% more clients and 30% more worksite employees than in the same period in 2020.
We are forecasting a 19% to 48% increase in Q4 adjusted EBITDA to a range of $45 million to $56 million and a 24% to 65% increase in adjusted earnings per share to a range of $0.61 to $0.81.