What is the NOI yield on the international tower and DAS properties in the second quarter 
increases, mobile network operators continue to deploy meaningful wireless capex. Service providers in the international markets, where we have a presence, are expected to spend approximately $30 billion on their networks in 2020, in essence doubling the TAM of our U.S. market alone.
With mobile broadband penetration growing, we continue to expect to generate higher organic growth rates internationally than in the United States over the long term, while driving meaningful expansion in our international return on invested capital. Fundamentally, we are utilizing our international strategy to increase and extend our overall global return profile. The ongoing COVID-19 pandemic has served to further highlight the criticality of wireless connectivity internationally, particularly in markets where fixed-line penetration is minimal. Unlike in the United States, where most of us are plugging into our Wi-Fi-enabled fixed-line connections as we work from home, mobile networks serve as the backbone of virtually all work-from-home functions in these international locations.
And as you can imagine, broad-based stay-at-home orders and other restrictions that have been implemented in these markets over the last several months have led to additional strain on existing mobile networks. For example, Vodafone Idea in India noted that they experienced a year's worth of data traffic across their network in a single week following the implementation of lockdown measures. Similarly, major carriers across Latin America, Africa and Europe have outlined significant spikes in data usage, and regulators have allocated additional temporary spectrum and implemented other policies to help maintain connectivity. As I mentioned earlier, we are committed to doing everything we can to support our tenants as they deal with the strain of this increased usage on their networks.
Now I'd like to take a few minutes to discuss the attractive economics that we were driving across our international business. In the second quarter, our international operations accounted for roughly 43% of our property revenue and about one-third of our property operating profit. Our international tower and DAS properties drove an annualized cash gross margin of over $1.8 billion in the quarter, resulting in a nearly 9.5% NOI yield on our more than $19 billion in total international tower and DAS investments, as you can see on Slide 6 of our earnings presentation. This NOI yield includes both sites that we have recently acquired as well as sites that have been in our portfolio for a number of years, benefiting from long-term tenancy and revenue growth.
Our most seasoned vintage of international sites, those built or acquired prior to 2010, is yielding approximately 24% in U.S. dollar terms, illustrating the power of operating leverage within our business. We view this type of return profile as a clear indication that international tower assets have the capacity to drive economics that are equal to or better than the United States' tower model over the long term. Importantly, I'll note that the NOI yield numbers I'm referencing today are U.S.
dollar equivalents, that is, they take into account any foreign currency devaluation in the numerator while freezing the denominator at historical exchange rates in the period in which the sites were acquired or built. Over the last 20 years, especially since 2007, we have been steadily growing our international portfolio with a focus on macro towers in some of the largest free-market democracies worldwide. Through a combination of our highly efficient new build programs and selective acquisitions, including the Eaton Towers deal we closed at the end of last year, we've added more than 130,000 international sites in just the last decade, including more than 24,000 sites we built ourselves. These sites typically have lower initial returns due to lower initial tenancy.
You can see this on the slide, where sites we've added to our international portfolio between 2010 and '14 are generating yields of 10%, and those added since 2015 are generating yi
increases, mobile network operators continue to deploy meaningful wireless capex. Service providers in the international markets, where we have a presence, are expected to spend approximately $30 billion on their networks in 2020, in essence doubling the TAM of our U.S. market alone.
With mobile broadband penetration growing, we continue to expect to generate higher organic growth rates internationally than in the United States over the long term, while driving meaningful expansion in our international return on invested capital. Fundamentally, we are utilizing our international strategy to increase and extend our overall global return profile. The ongoing COVID-19 pandemic has served to further highlight the criticality of wireless connectivity internationally, particularly in markets where fixed-line penetration is minimal. Unlike in the United States, where most of us are plugging into our Wi-Fi-enabled fixed-line connections as we work from home, mobile networks serve as the backbone of virtually all work-from-home functions in these international locations.
And as you can imagine, broad-based stay-at-home orders and other restrictions that have been implemented in these markets over the last several months have led to additional strain on existing mobile networks. For example, Vodafone Idea in India noted that they experienced a year's worth of data traffic across their network in a single week following the implementation of lockdown measures. Similarly, major carriers across Latin America, Africa and Europe have outlined significant spikes in data usage, and regulators have allocated additional temporary spectrum and implemented other policies to help maintain connectivity. As I mentioned earlier, we are committed to doing everything we can to support our tenants as they deal with the strain of this increased usage on their networks.
Now I'd like to take a few minutes to discuss the attractive economics that we were driving across our international business. In the second quarter, our international operations accounted for roughly 43% of our property revenue and about one-third of our property operating profit. Our international tower and DAS properties drove an annualized cash gross margin of over $1.8 billion in the quarter, resulting in a nearly 9.5% NOI yield on our more than $19 billion in total international tower and DAS investments, as you can see on Slide 6 of our earnings presentation. This NOI yield includes both sites that we have recently acquired as well as sites that have been in our portfolio for a number of years, benefiting from long-term tenancy and revenue growth.
 Our most seasoned vintage of international sites, those built or acquired prior to 2010, is yielding approximately 24% in U.S. dollar terms, illustrating the power of operating leverage within our business. We view this type of return profile as a clear indication that international tower assets have the capacity to drive economics that are equal to or better than the United States' tower model over the long term. Importantly, I'll note that the NOI yield numbers I'm referencing today are U.S.
dollar equivalents, that is, they take into account any foreign currency devaluation in the numerator while freezing the denominator at historical exchange rates in the period in which the sites were acquired or built. Over the last 20 years, especially since 2007, we have been steadily growing our international portfolio with a focus on macro towers in some of the largest free-market democracies worldwide. Through a combination of our highly efficient new build programs and selective acquisitions, including the Eaton Towers deal we closed at the end of last year, we've added more than 130,000 international sites in just the last decade, including more than 24,000 sites we built ourselves. These sites typically have lower initial returns due to lower initial tenancy.
You can see this on the slide, where sites we've added to our international portfolio between 2010 and '14 are generating yields of 10%, and those added since 2015 are generating yi