Throughout the last 18 months, our franchisees have continued to step up to the challenge in service to their customers, their communities and their team members.
During the second quarter, we delivered 17.1% global retail sales growth, excluding foreign currency impact, driven by a powerful combination of growth in US same-store sales, international same-store sales and global store counts.
We also reinforced our leadership position in the pizza category with a very strong quarter of global store growth, highlighted by the opening of our 18,000th store.
When you look at it on a trailing four-quarter basis, our pace of net store growth is increased from 624 in Q4 2020 to 884 in Q2 2021.
During the quarter, we also completed our $1.85 billion refinancing transaction, lowering the cost of our debt and giving us the capacity to return $1 billion to our shareholders through our recently completed accelerated share repurchase transaction.
Overall, Domino's team members and franchisees around the world generated impressive operating results, leading to a diluted earnings per share of $3.06 for Q2.
Our diluted earnings per share as adjusted for certain items related to our recapitalization transaction completed during the quarter with $3.12.
Global retail sales grew 21.6% in Q2, as compared to Q2 2020.
When excluding the positive impact of foreign currency, global retail sales grew 17.1%.
Breaking down total global retail sales growth, US retail sales grew 7.4% and international retail sales grew 39.7%.
When excluding the positive impact of foreign currency, international retail sales grew 29.5% rolling over a prior year decrease of 3.4%.
Turning to comps, during Q2, we continue to lead the broader restaurant industry with 41 straight quarters of positive US comparable sales and 110 consecutive quarters of positive international comps.
Same-store sales in the US grew 3.5% in the quarter lapping a prior-year increase of 16.1%.
Same-store sales for our international business grew 13.9% rolling over a prior year increase of 1.3%.
Breaking down the US comp, our franchise business was up 3.9% in the quarter, while our company-owned stores were down 2.6%.
Shifting to unit count, we and our franchisees added 35 net stores in the US during the second quarter, consisting of 39 store openings and foreclosures.
Our international business added 203 net stores comprised of 217 store openings and 14 closures.
Total revenues for the second quarter were up approximately $112.4 million or 12.2% over the prior year quarter.
Changes in foreign currency exchange rates positively impacted our international royalty revenues by $4 million in Q2 2021 as compared to the prior year quarter.
Our consolidated operating margin as a percentage of revenues increased to 39.5% in Q2 2021 from 38.8% in the prior year, due primarily to higher revenues from our US franchise business.
Company-owned store margin as a percentage of revenues increased to 24.5% from 23.1% primarily as a result of lower labor costs, partially offset by higher food costs.
Supply chain operating margin as a percentage of revenues decreased to 11% from 11.9% in the prior year quarter, resulting primarily from higher insurance and food costs, as well as higher fixed operating costs driven by depreciation and our new supply chain facilities opened last year.
G&A expenses increased approximately $12.3 million in Q2 as compared to Q2 2020, resulting from higher labor costs, including higher variable performance-based compensation and non-cash compensation expense, partially offset by lower professional fees.
Net interest expense increased approximately $6.7 million in the quarter, driven by a higher average debt balance.
Our weighted average borrowing rate for Q2 2021 was 3.8%, down from 3.9% in Q2 2020.
Our effective tax rate was 19.6% for the quarter as compared to 4.7% in Q2 2020.
The effective tax rate in Q2 2021 includes a 2.3 percentage point positive impact from tax benefits on equity-based compensation.
This compares to an 18.5 percentage point positive impact in Q2 2020.
Combining all of these elements, our second quarter net income was down $2 million or 1.7% versus Q2 2020.
On a pre-tax basis, we were up $20.6 million or 16.5% over the prior year.
Our diluted earnings per share in Q2 was $3.06 versus $2.99 in the prior year.
Our diluted earnings per share as adjusted for the impact of the recapitalization transaction was $3.12, an increase of $0.13 or 4.3% over the prior year.
Breaking down that $0.13 increase in our diluted earnings per share as adjusted, most notably, our improved operating results benefited us by $0.53, net interest expense adjusted for the impact of the items affecting comparability I discussed previously negatively impacted us by $0.08, a lower diluted share count driven by share repurchases over the trailing 12 months benefited us by $0.12, and finally our higher effective tax rate, resulting from a lower tax benefits on equity based compensation negatively impacted us by $0.44.
During Q2, we generated net cash provided by operating activities of approximately $143 million.
After deducting for capex, we generated free cash flow of approximately $126 million.
Regarding our capital expenditures, we spent approximately $17 million on capex in Q2, primarily on our technology initiatives, including our next-generation point-of-sale system.
As previously disclosed, during Q2, we also entered into an accelerated share repurchase transaction for $1 billion.
We received and retired approximately 2 million shares at the beginning of the ASR.
The ASR settled yesterday and we received a retired an additional 238,000 shares in connection with this transaction.
In total, the average repurchase price throughout the ASR program was $444.29 per share.
We also paid a $0.94 quarterly dividend on June 30.
Subsequent to the end of the quarter, our Board of Directors declared a quarterly dividend of $0.94 per share to be paid on September 30.
We are focused on building the business for the long term and that long-term focus on great product, service, image and technology is precisely why we were able to deliver a terrific quarter, highlighted by 7.4% US retail sales growth, lapping 19.9% from Q2 2020.
Turning to same-store sales, perhaps the thing I'm most pleased about when I look at the 3.5% US comp is the fact that we were able to hold orders flat while overlapping the big gains from Q2 2020.
At 19.6% for Q2, we saw a material sequential improvement of the two-year stack when compared to the first quarter.
Beyond the comps, when you look at the absolute dollars, our second quarter same store average weekly unit sales in the US exceeded $27,000, another sequential uptick from the levels seen in the first quarter.
Now turning to the other critical component of our retail sales growth, new store openings, our addition of 35 net stores was softer than we expected.
We ran a brief 49% off car-side delivery awareness campaign during the quarter and just recently launched a campaign highlighting our Car Side Delivery 2-Minute Guarantee.
Our franchisees and operators have fully embraced car side delivery and we are consistently averaging below 2 minutes out the door and on our way to the customer's cars.
Our 29.5% international retail sales growth, excluding foreign currency impact was supported by an exceptional 13.9% comp, continuing the momentum we had in the first quarter.
As I discussed earlier with our US business, we're also watching the two-year comp stacks for international, anchoring back to pre-COVID 2019 and we'll continue to do so throughout 2021.
Q2 represented a 15.2% two-year stack, a sequential improvement over the first quarter.
I'm particularly pleased with our strong momentum on store growth as international provides a significant push toward our two to three-year outlook of 6% to 8% global net unit growth.
Our 203 net stores in Q2 increased our trailing four quarter pace of international store growth to 653 net stores.
At the end of the quarter, we had fewer than 175 temporary store closures, with many of those located in India, which has been hit particularly hard by COVID.
This included a cross-functional team that provided employee assistance 24/7 as well as several COVID isolation centers with oxygen concentrator banks.
China passed the 400 store milestone during Q2 and once again Dash, our master franchise partner delivered outstanding retail sales growth for the brand.
Japan reached the 800 store milestone in the weeks following the close of our second quarter and continued the outstanding performance under master franchisee Domino's Pizza Enterprises ownership.

Summary:
Overall, Domino's team members and franchisees around the world generated impressive operating results, leading to a diluted earnings per share of $3.06 for Q2.
Our diluted earnings per share as adjusted for certain items related to our recapitalization transaction completed during the quarter with $3.12.
Same-store sales in the US grew 3.5% in the quarter lapping a prior-year increase of 16.1%.
Same-store sales for our international business grew 13.9% rolling over a prior year increase of 1.3%.
Our diluted earnings per share in Q2 was $3.06 versus $2.99 in the prior year.
Our diluted earnings per share as adjusted for the impact of the recapitalization transaction was $3.12, an increase of $0.13 or 4.3% over the prior year.
Our 29.5% international retail sales growth, excluding foreign currency impact was supported by an exceptional 13.9% comp, continuing the momentum we had in the first quarter.
As I discussed earlier with our US business, we're also watching the two-year comp stacks for international, anchoring back to pre-COVID 2019 and we'll continue to do so throughout 2021.