In recognition of the efforts and the unique challenges posed by the pandemic, we invested over $100 million in incremental financial assistance for our frontline hourly associates in the quarter, which brought our total COVID-related support for hourly associates to over $900 million for the year.
And in the quarter, we invested $65 million in support of store safety protocols and our communities.
For the year, we invested nearly $1.3 billion in COVID-related support for our associates, store safety and our communities.
For the quarter, we delivered total company comparable sales growth of 28% over the prior year and 41% growth in adjusted diluted earnings per share to $1.33.
Those results cap off a fiscal 2020 where comp sales increased 26% and adjusted earnings per share grew 54% to $8.86.
Looking at the fourth-quarter results from a geographic perspective in the U.S., growth was broad-based, with comparable sales growth exceeding 19% across all 15 geographic regions and exceeding 25% for all U.S. divisions.
On lowes.com, sales grew 121% as customers shifted more of their shopping online, especially over the holiday season.
And Pro continues to show strong momentum, evidenced by the mid-20s comp in the quarter and nearly a 20% comp for the year.
1 Most Admired Specialty Retailer, bestowing that honor on Lowe's for the first time in 17 years.
1 priority, which is supporting the health and safety of our associates and our customers.
We delivered U.S. home improvement comparable sales growth of 28.6% in the fourth quarter.
In fact, all 15 merchandising departments generated positive comps of over 16%.
Several other categories posted comps above 30%, including building materials, which was driven by strong demand for roofing and gutters.
Our seasonal and outdoor living, lawn and garden and paint categories also delivered comps above 30% in the quarter, reflecting the consumers' continued focus on the home.
As Marvin mentioned, we delivered sales growth of 121% on lowes.com, our third consecutive quarter with over 100% comps online.
As we discussed last quarter, we have been resetting the layout of our U.S. stores with approximately 95% of our resets now complete.
In recognition of the outstanding efforts of our associates, in January, we announced a bonus of $300 for each full-time associate and $150 for each part-time associate.
This $80 million bonus brought the total COVID-related assistance to our associates to over $900 million in 2020.
And I could not be more pleased to announce today that for the fourth quarter in a row, 100% of our stores are under "Winning Together" profit-sharing bonus totaling $90 million.
And because of their efforts, once again exceeded expectations, this represents an incremental $30 million over the target payment level.
And we're supporting our communities again through hiring as we bring on more than 50,000 seasonal and full-time retail associates this spring to ensure that our customers get the exceptional service they expect from Lowe's.
This builds on the more than 90,000 associates hired into permanent roles over the past year.
Nowhere is this more evident than the 111% sales growth on Lowes.com for the year.
And with roughly 60% of these online orders fulfilled in our stores, we needed to dramatically expand our fulfillment capabilities to support this increased demand.
We now have BOPIS lockers in over 1,200 stores with the goal of rolling out lockers to all U.S. stores by April.
As a true partner to the Pro, we are now providing our Pro loyalty members with a $100 discount on TurboTax.
Our Pro loyalty members can also export up to 24 months of transaction history, expediting their year-end close process.
These perpetual productivity improvements will help us to move toward our multiyear goal of achieving $2.5 billion to $2.7 billion in store opex productivity that we set at the December investor update.
In fiscal 2020, we generated $9.3 billion in free cash flow driven by outstanding operating performance, and we returned $6.7 billion to our shareholders through both a combination of share repurchases and dividends.
During the fourth quarter alone, we paid $452 million in dividends at $0.60 per share.
We also repurchased 21.1 million shares for $3.4 billion at an average price of approximately $160 a share.
This brings the total to $5 billion in share repurchases for the year.
We have approximately $20 billion remaining on our share repurchases authorization and plan to utilize our strong cash flow to drive significant long-term shareholder value.
Capital expenditures totaled $619 million in the quarter and $1.8 billion for the full year as we invest in the business to support our strategic growth initiatives.
We ended 2020 with $4.7 billion of cash and cash equivalents on the balance sheet.
And along with $3 billion in undrawn capacity on our revolving credit facility, we have immediate access to $7.7 billion in funds.
At the end of the fiscal year, our adjusted debt-to-EBITDA ratio stands at 2.2 times.
In Q4, we generated GAAP diluted earnings per share of $1.32 compared to $0.66 last year, an increase of 100%.
In Q4, we delivered adjusted diluted earnings per share of $1.33, an increase of 41% compared to the prior year.
Q4 sales were $20.3 billion, driven by a comparable sales increase of 28.1%.
This was due to comparable store average ticket growth of 14.2% and transaction growth of 13.9%, with strong repeat rates from both new and existing customers.
Commodity inflation drove a benefit of approximately 300 basis points to comps in the quarter as lumber continues to experience rising prices.
U.S. comp sales were up 28.6% in the quarter.
Our U.S. monthly comps accelerated through the quarter, were 23.8% in November, 28% in December and 35.7% in January.
Adjusted gross margin was 31.8%, down eight basis points from last year.
Despite cycling over significant improvements last year in our process to more effectively manage product margin, product gross margin rate improved 125 basis points driven by continued execution on our pricing, cost management and promotional strategies.
These benefits to adjusted gross margin were offset by 40 basis points of pressure from inventory shrink, 40 basis points of pressure from supply chain cost, 35 basis points of pressure from lumber installation and 20 basis points of pressure from lower credit revenue.
Adjusted SG&A of 22.3% levered 42 basis points to 2019.
As we anticipated, we incurred approximately $165 million of COVID-related expenses.
These investments included approximately $100 million in financial assistance for our frontline associates and approximately $60 million related to cleaning and other safety-related programs, as well as approximately $5 million in charitable contributions.
These $165 million of COVID-related expenses negatively impacted SG&A leverage by approximately 80 basis points.
As expected, we incurred approximately $150 million in the U.S. stores reset project, which negatively impacted SG&A leverage by approximately 75 basis points.
As Bill mentioned, the resets have been completed in approximately 95% of our stores.
These incremental costs were offset by payroll leverage of approximately 105 basis points related to higher sales volume and improved store operating efficiencies, occupancy leverage of approximately 30 basis points and advertising leverage of approximately 25 basis points.
Adjusted operating income margin of 7.6% of sales for the quarter was up 41 basis points to the prior year as operational productivity improvements were offset somewhat by significant investments in our stores and supply chain to drive long-term growth.
The adjusted effective tax was 25.8%.
At year end, inventory was $16.2 billion, and lumber inflation increased inventory values by approximately $240 million.
These three market scenarios would result in total sales expectations ranging from $82 billion to $86 billion for the year.
Additionally, in each scenario, we expect our adjusted operating margin to increase year over year, ranging from 11.2% to 12%, depending upon the demand environment.
And consistent with my comments at the investor update in December, embedded in each of these scenarios are the incremental investments in frontline associate wages and equity programs that totaled $1.4 billion through 2019 and 2020.
This scenario assumes the relevant home improvement market will experience a modest contraction this year, and our sales would approach $86 billion.
And consistent with what we outlined at Investor Day, we are expecting $9 billion in share repurchases this year.
And we are planning for approximately $2 billion in capital expenditures in '21.

Summary:
For the quarter, we delivered total company comparable sales growth of 28% over the prior year and 41% growth in adjusted diluted earnings per share to $1.33.
Those results cap off a fiscal 2020 where comp sales increased 26% and adjusted earnings per share grew 54% to $8.86.
We delivered U.S. home improvement comparable sales growth of 28.6% in the fourth quarter.
In Q4, we generated GAAP diluted earnings per share of $1.32 compared to $0.66 last year, an increase of 100%.
In Q4, we delivered adjusted diluted earnings per share of $1.33, an increase of 41% compared to the prior year.
Q4 sales were $20.3 billion, driven by a comparable sales increase of 28.1%.
And consistent with what we outlined at Investor Day, we are expecting $9 billion in share repurchases this year.