In 2020, we suffered 470 infections, 15 hospitalizations and sadly, three deaths.
With over a half century of outstanding performance, CCM's influence on our overall performance has consistently expanded despite our diversification efforts peaking in 2020 when it accounted for over 70% of revenues and over 90% of earnings.
A consistent 30% plus returns business, CCM's performance warranted and earn the right to share the majority of investment dollars that were allocated to portfolio diversification.
CCM products provide a substantial offset to the estimated 40% of greenhouse gases globally generated from the construction and maintenance of buildings and our teams are focused on continuing to support the growing efforts in global energy efficiency.
Non-residential buildings built 10 to 20 years ago make up over 25% of current infrastructure and those roofs will need replacing in the next decade.
Aided by the Carlisle experience and our market position, CCM should continue to capture placement of installed roofing systems and grow share with new energy-efficient, labor reducing and cost-effective product and solutions in the $6 billion and growing market.
Third, like Polyurethane, Architectural Metals is an exciting new platform for CCM, it's a $1 billion market growing at approximately 2 times GBP provides an attractive opportunity to diversify into the sloped roof market with a highly sustainable product.
Metal roofs are 100% recyclable, increase energy efficiency of the building up to 20% versus traditional materials and reduce waste in the manufacturing process.
Fourth, we are committed to accelerating growth in Europe, a $10 billion -- or EUR10 billion addressable market.
To drive this growth, we recently changed leadership in the region and announced the investment of over $25 million to expand capacity in our German manufacturing facility.
We've generated $2.5 billion of free cash flow over the last six years and recently accelerating significantly with almost half of that was generated in 2019 and 2020.
This is evidenced by our deployment of more of than $380 million of share repurchases in 2020, totaling approximately $1.5 billion in share repurchases since 2017.
And at our latest Board meeting, our Board approved an incremental $5 million share repurchase authorization for Carlisle.
We also returned over $112 million to shareholders in the form of dividends in 2020, raising our dividend in August for the 44th consecutive year.
An finally, we spent $96 million of capex in 2020 and that plans to significantly increase that in 2021.
In 2020, we also made progress in diversity and inclusion exiting 2020 with 50% of our Board of Directors identifying as gender, racially or ethnically diverse and meeting our 2020 target for percent of females in senior leadership positions.
In 2020, COS delivered savings of 1.3% of sales, well within our Vision 2025 annual target of 1% to 2%, a remarkable feat considering 2020's challenging conditions and proving that Carlisle employees truly embody and live our continuous improvement culture every day.
Revenue decreased 7% to $1.1 billion in the fourth quarter.
Organic revenue declined 9%.
Acquisitions contributed 1.4% of sales growth for the quarter and FX was a 60 basis point tailwind.
Q4 operating margin declined 180 basis points, pricing and volume headwinds combined for a 320 basis point decline and acquisitions were a 40 basis point tailwind.
Offsetting these declines, freight, labor, raw material, other operating costs netted to a 60 basis point improvement.
COS benefits added 120 basis points.
On Slide 15, we have provided an earnings per share bridge where you can see the fourth quarter diluted earnings per share from continuing operations was $1.57, which compares to $1.81 last year.
Volume, price and mix combined were a $0.74 year-over-year decrease.
Partially offsetting, interest and tax contributed $0.09 and raw material, freight and labor costs netted to a $0.16 benefit.
Share repurchases contributed $0.09, COS contributed $0.19, and finally, operating expenses were a $0.03 headwind.
At CCM, the team again delivered outstanding results with revenues increasing 1% driven by volume and 30 basis points of foreign currency translation tailwind.
Operating margin at CCM was a record 20.4% for the fourth quarter, a 350 base improvement over the last year driven by CCM team's superb cost management and COS partially offset by wage inflation.
CCM executed well in delivering approximately $15 million of net price cost realization in the quarter.
CIT's revenue declined 35.4% in the fourth quarter.
In other positive recent news, the 737 MAX 8 has been cleared for returned flights in the U.S., Europe and South America, while TSA, the early checkpoint data continues to improve.
CIT's operating margin declined significantly year-over-year to a negative 8.6% driven by commercial aerospace volume declines and accelerated restructuring actions.
CFT sales declined 8.3% year-over-year.
Organic revenue declined 16.1% and additionally, acquisitions added 5% in the quarter.
FX contributed 280 basis points.
Operating income of 4.5% was an 820 basis point decline year-on-year.
CBF's fourth quarter organic revenue grew 2.8% and FX had a positive 2.6% impact driving CBF growth of 5.4% in the quarter.
Operating income was $8 million or 1.1% operating margin.
On slides 20 and 21, we show selected balance sheet metrics.
We ended the quarter with $902 million of cash on hand and $1 billion of availability under our revolving credit line.
Free cash flow for 2020 was an exceptional $601 million consistent with '19 results on the lower sales volumes.
Corporate expense is expected to be approximately $105 million for the year.
We expect depreciation and amortization expense to be approximately $225 million.
For the full year, we will continue to invest in our businesses and now expect capital expenditures of $100 million to $175 million.
Net interest expense is approximately -- expected to be approximately $75 million for the year and we expect our tax rate to be approximately 25%.
We'll continue to deploy capital into strategic acquisitions, share repurchases and dividends, all the while maintaining our commitment to delivering returns on invested capital in excess of 15% and ultimately driving the $15 of earnings per share.

Summary:
On Slide 15, we have provided an earnings per share bridge where you can see the fourth quarter diluted earnings per share from continuing operations was $1.57, which compares to $1.81 last year.
Operating income was $8 million or 1.1% operating margin.