Finally, all references in today's remarks to tobacco consumers or consumers within a specific tobacco category or segment refer to existing adult tobacco consumers 21 years of age or older.
First, Altria grew its 2021 adjusted diluted earnings per share by 5.7% driven in part by the resiliency of our cigarette, cigar and moist smokeless tobacco businesses.
Additionally, we returned more than $8.1 billion in cash to shareholders through dividends and share repurchases.
This total represents the third largest single year cash return in Altria's history and the largest annual return since 2002.
2021 was a dynamic year for the U.S. tobacco industry and total industry volumes were influenced by several factors, including pandemic-induced shifts in consumer purchasing behavior and tobacco usage occasions, a continued trend toward smoke-free alternatives and an evolving regulatory and legislative landscape.
Despite year-over-year volatility due to pandemic-related factors, total tobacco volume trends remained stable.
In fact, we estimate that overall tobacco space volumes have decreased by 0.3% annualized for the past two years and by 0.8% over the last five years on a compounded annual basis.
Diving deeper, total estimated equivalized volumes for smoke-free products in the U.S. grew to 3.8 billion equivalized units in 2021 and represented approximately 24% of the total tobacco space.
And in combustibles, volume declined to approximately 11.8 billion equivalized units driven by several factors, which Sal will discuss later in his remarks.
retail share of oral tobacco increased by nearly a full share point sequentially, reaching 3.9 share points for the fourth quarter and nearly doubling its share over the past six months.
was available for sale in approximately 117,000 U.S. retail stores.
nicotine pouch category reached a total oral tobacco retail share of 17.9 percentage points in the fourth quarter, growing 7.4 share points year over year.
In heated tobacco, our teams made excellent progress with IQOS in the Northern Virginia market, with Marlboro HeatSticks achieving a 1.9% retail share of the cigarette category in stores with distribution for the month of October.
The latest data shows that JUUL underage usage is down by 70% from 2019, with total underage nicotine vaping down 27% over the same period.
Taking these factors into consideration, we expect to deliver 2022 full year adjusted diluted earnings per share in a range of $4.79 to $4.93.
This range represents an adjusted diluted earnings per share growth rate of 4% to 7% from a $4.61 base in 2021.
We expect 2022 adjusted diluted earnings per share growth to be weighted toward the second half of the year.
In the fourth quarter, the segment grew its adjusted OCI by 4.9% and expanded its adjusted OCI margins to 56.2%.
The segment also reported strong net price realization of 8.8%.
Fourth quarter smokeable segment reported domestic cigarette volumes decline by 5.9%.
When adjusted for trade inventory movements and other factors, we estimate that segment domestic cigarette volumes for the fourth quarter declined by 8% and that industry volumes declined by 6.5% over the same period.
As a reminder, adjusted cigarette volumes were strong in the fourth quarter of 2020, with our smokeable segment adjusted cigarette volumes declining by just 1% and industry volumes growing by one half percent.
For the full year, smokeable segment adjusted OCI grew 3.1% to $10.4 billion.
Adjusted OCI margins expanded by 1.2 percentage points to 57.6%.
These strong full year results were supported by robust net price realization up 9.1%.
Full year smokable segment reported domestic cigarette volumes declined 7.5% due to the strong comparison period and the continuation of pandemic driven changes in the consumer behavior.
When adjusted for trade inventory movement, calendar differences and other factors, we estimate that smokable segment cigarette volumes declined by 6% and that the full industry declined by 5.5%.
In fact, the two-year average decline rates for adjusted smokable segment and industry cigarette volume declines were 4% and 3%, respectively, well within the range of historic norms.
We remain focused on the long-term strength of Marlboro and we are very pleased that its full year share grew 0.2 to 43.1% and that the brand remained stable since the beginning of the pandemic.
In discount, total segment retail share in the fourth quarter continued to fluctuate, increasing 0.7 sequentially to 26% driven primarily by deep discount products.
For the full year, discount segment share increased five-tenths to 25.4%, which was at the high end of its historical ranges.
When adjusted for trade inventory movements and calendar differences, we estimate that total oral tobacco segment volumes declined by 0.5%.
nearly offset declines in MST. The segment declined 1.6 percentage points versus the fourth quarter last year due to the continued growth of the oral nicotine pouch category.
We recorded $172 million of adjusted equity earnings in the fourth quarter, representing Altria's share of ABI's third quarter results.
For the full year, we recorded $639 million in adjusted equity earnings, up 18.3% versus 2020.
At year-end, the net finance assets balance was $114 million, down more than $200 million since the end of 2020 due to rents received and asset sales.
These record cash returns included paying $6.4 billion in dividends, raising the dividend for the 56th time in 52 years and repurchasing nearly 36 million shares during the year totaling $1.7 billion.
Michelle Wine Estates and expanded our share repurchase program from $2 billion to $3.5 billion.
We have approximately $1.8 billion remaining under this expanded program, which we expect to complete by December 31, 2022.
As of year-end, our debt to EBITDA ratio was 2.3 times and our weighted average coupon was 4%.

Summary:
2021 was a dynamic year for the U.S. tobacco industry and total industry volumes were influenced by several factors, including pandemic-induced shifts in consumer purchasing behavior and tobacco usage occasions, a continued trend toward smoke-free alternatives and an evolving regulatory and legislative landscape.
Despite year-over-year volatility due to pandemic-related factors, total tobacco volume trends remained stable.
In fact, we estimate that overall tobacco space volumes have decreased by 0.3% annualized for the past two years and by 0.8% over the last five years on a compounded annual basis.
Taking these factors into consideration, we expect to deliver 2022 full year adjusted diluted earnings per share in a range of $4.79 to $4.93.
We expect 2022 adjusted diluted earnings per share growth to be weighted toward the second half of the year.
Fourth quarter smokeable segment reported domestic cigarette volumes decline by 5.9%.
At year-end, the net finance assets balance was $114 million, down more than $200 million since the end of 2020 due to rents received and asset sales.