Google has caught up to Facebook in a key area (GOOG, FB, GOOGL)

Getting people to download apps is a big business and Google just upped its ante. 

Over the past several years, mobile app install ads have swelled in popularity because they drive significant downloads and have a clear return on investment for developers. 

Facebook in particular has seemed to dominate this area, partially through ad placement on the prime real estate of its News Feed. 

But Google just announced at its I/O developers' conference that it has now driven more than 2 billion app installs, the same number than Facebook announced at its own developers' conference in April. On the search giant's end, that's a significant improvement from last year, when it claimed only "hundreds of millions" to Facebook's 1 billion app installs.

Although Facebook is expected to have higher net display ad revenues than Google, according to eMarketer, the search giant's growth in this area seems strong. 

"We've more than doubled our volume," Sissie Hsiao, product management director for mobile app ads, tells Business Insider. 

She attributes that growth to increased simplicity in Google's universal app campaign tool, which helps developers place ads across the Google Play Store, search, YouTube, and its Display Network. The company is now expanding the previously Android-only tool to iOS, with the program launching in beta today. 

Google is also now expanding its tool to allow developers to target more "high quality" users. Instead of optimizing for the number of installs, they can choose to specify that they want users who will hit a specific conversion, like getting to a certain level in a game, or actually booking a vacation. 

"Instead of now just giving us their app and their price, they can give us their app, the price that they want to acquire the highest value user at, and the action that is of high value," Hsiao says. 

By expanding its universal ad campaigns, Google makes itself an even more attractive to option to developers, and sets itself up to capture more of the mobile app install ad spending, which BI Intelligence estimates will reach $5.4 billion in 2016 in the US alone, rising to as much as $6.8 billion in 2019.

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