Robust retail demand for our products has driven field inventory to the lowest level in decades at just over 10 weeks on hand.
The panel of judges praise Brunswick and Mercury for a record setting 2021, filled with multiple industry-changing product launches such as the V-12 600-horsepower Verado outboard engine and the Sea Ray 370 Sundancer among others.
Of the thousands of companies eligible for this recognition, Brunswick was one of only 750 companies selected to receive the award, ranking in the top 10 companies in the world within the engineering and manufacturing category.
Since 2019, Freedom has seen notable increases in the ethnic diversity of our members, which grew from around 10% in 2019 to 15% now and the percentage of women making up our total member base, which grew by 130 basis points to 35%.
Also, a particular note, the percentage of Hispanic Freedom members almost doubled to 8.4% in 2021 from 4.7% in 2018.
Of those surveyed, approximately 60% worked remotely at least partially, and 44% of those polled have been able to fit boating into their work week this season, with more than 20% actually working from their boat at some time.
Over the last two years, Mercury has gained an extraordinary 310 basis points of U.S. retail market share with outsized gains in higher horsepower products, where a significant amount of investment has been made in recent years.
Despite supply chain challenges, cost inflation and labor tightness at our suppliers and some of our own facilities during the quarter, we anticipate annual unit production of greater than 95% of our original production plan for the year, with shortages and delays primarily constraining additional upside.
By comparison, our Propulsion business is anticipated to produce approximately 110% of its original 2021 production schedule.
Freedom is now approaching 320 global locations and 47,000 memberships networkwide with more than 4,000 boats in its overall fleet, including an increasing percentage of Brunswick boats and engines.
Except for Asia Pacific, we saw sales normalize slightly in the third quarter but still up 26% versus the same period in 2019.
Domestic sales grew 14%, with international sales up 17% versus the prior year.
The result is a reported 8% decline in main powerboat retail unit sales year-to-date when compared with the same period in 2020 but still 3% greater than the same period in 2019.
Outboard engine unit registrations were down 6% through the first nine months of 2021 when compared with the same period in 2020, with Mercury outperforming the industry.
For example, all of our 2022 model year and 80% of our 2022 calendar year production slots are already sold out.
When compared with 2020, third quarter net sales were up 16% with adjusted operating margins of 15.5%.
Operating earnings on an as-adjusted basis increased by 9%, and adjusted earnings per share was $2.07, once again setting new all-time highs for any third quarter for which we have available records.
First nine month comparisons are also very favorable, with 2021 net sales up 39% when compared with the first nine months of 2020 and adjusted operating margins of 16.5%, a 290 basis point improvement from 2020.
This resulted in adjusted earnings per share for the first nine months of $6.82 and a very robust operating leverage of 24%.
We have generated almost $300 million of free cash flow through the first nine months of the year, which is a strong result considering the incremental working capital needed to satisfy increased needs for inventory as we elevate production levels and the $60 million increase in capital spending when compared to the same prior year period.
Revenue in the Propulsion business increased 19% versus the third quarter of 2020 and was up 58% versus Q3 of 2019.
Operating margins were flat versus 2020 but up 320 basis points versus Q3 of 2019 as pricing, favorable absorption and benefits from more favorable sales mix were able to offset higher manufacturing costs, primarily caused by material inflation.
In our Parts and Accessories segment, revenues increased 7%, and adjusted operating earnings were up 2% versus the third quarter of 2020.
Adjusted operating margins of 22.2% were down 120 basis points when compared with the prior year quarter and were negatively impacted by the closure of a key manufacturing and distribution location in New Zealand for a significant portion of the quarter due to national COVID lockdowns as well as increased spending on growth-related investments.
In our Boat segment, sales were up 22% and adjusted operating margins were down 230 basis points to 6.9% when compared with the third quarter of 2020.
When compared to the third quarter of 2019, sales were up 45%, and adjusted operating margins were up 240 basis points.
Freedom Boat Club, which is included in Business Acceleration, contributed approximately 3% of the segment's revenue at a margin profile that continues to be accretive to the segment.
As Dave mentioned earlier, we believe our boat production will reach at least 95% attainment of our original production plan for 2021, a remarkable achievement given the current supply constrained environment we are working in.
As a result, we wholesale sold approximately 8,200 boats during the third quarter, which was roughly the same number of units sold at retail and 16% greater than the number of units wholesale sold in the third quarter of 2020.
This keeps dealer inventories at an all-time low of approximately 7,400 units.
Our boat brands ended September with just over 10 weeks of boats on hand, measured on a trailing 12-month basis, with units in the field lower by 27% versus the same time last year.
We anticipate the U.S. marine industry retail unit demand for the full year to improve from reported year-to-date levels, ending at close to flat versus 2020, net sales of approximately $5.8 billion, adjusted operating margin growth between 150 and 180 basis points, operating expenses as a percent of sales to remain lower than 2020, free cash flow in excess of $425 million and adjusted diluted earnings per share of approximately $8.15, which represents a 61% increase over 2020.
Note that we believe acquisitions will contribute about 10% of the fourth quarter's revenue growth but will be neutral on earnings per share after including the impact of additional interest costs related to the financing of the Navico transaction.
The only meaningful update relates to our effective tax rate for the year due to some favorability related to foreign branch income and certain state tax law changes, we now believe our effective tax rate for 2021 will be approximately 21.5%, which is slightly lower than our estimate from the July call.
Similarly, our capital strategy assumptions have not materially changed with the execution of the financing for the Navico transaction, creating a slightly higher interest expense for the year, with approximately $25 million of additional debt retired as a result of the tendering of our 2023 and 2027 notes during the financing process.
We anticipate ending the year with debt leverage of 1.7 times on a gross basis and below 1.5 times on a net basis.
Additionally, our $43 million of share repurchases in the third quarter brings our total share repurchases for the year to just shy of $100 million, and we have adjusted our guidance to show that we anticipate reaching approximately $120 million worth of share repurchases by the end of the year.
Freedom also continues to expand its footprint with the recent acquisition of the Connecticut territory, which has seven locations and over 600 memberships.
The feedback in Cannes from our channel partners and end consumers on the new V-12 600-horsepower Verado and our new boat models was extremely positive.
Sea Ray also reported a 65% increase in its revenue versus the 2019 show, while all other Brunswick brands on display reported strong consumer interest and sales.

Summary:
Despite supply chain challenges, cost inflation and labor tightness at our suppliers and some of our own facilities during the quarter, we anticipate annual unit production of greater than 95% of our original production plan for the year, with shortages and delays primarily constraining additional upside.
Except for Asia Pacific, we saw sales normalize slightly in the third quarter but still up 26% versus the same period in 2019.
Operating earnings on an as-adjusted basis increased by 9%, and adjusted earnings per share was $2.07, once again setting new all-time highs for any third quarter for which we have available records.
In our Parts and Accessories segment, revenues increased 7%, and adjusted operating earnings were up 2% versus the third quarter of 2020.