Singular, a mobile attribution and campaign analytics platform, has released its annual ROI Index that ranks global return on investment across mobile platforms. Google AdWords yielded the best return on investment (ROI) on Android devices in 2017, but Facebook still holds the top spot across iOS devices worldwide. For game marketers, iOS provided the highest return, but Android is closing the gap.

Ranks are Calculated based on 30-day ROI taking into account revenue, cost and fraud.

Previously, Facebook held the top spot across both Android and iOS platforms in terms of ROI, but Google AdWords took the lead in 2017. This was the case across all regions except Europe, the Middle East and Africa (EMEA). There, Google was out-shined by Facebook, Unity and Vungle at first, second and third place, respectively.

Mobile marketing ROI varied depending on whether the campaign was gaming-related. Apple’s iOS yielded 1.2 times higher return for mobile game marketers than Android in 2017. Non-gaming marketers experienced similar ROI on both platforms. Android is catching up, however, driving eight percent annual growth in ROI since 2016.

Spending on Twitter marketing increased across both iOS and Android devices last year. Compared to 2016, marketers achieved improved ROI on Twitter in 2017, especially among non-gaming campaigns. Twitter delivered the second highest ROI in 2017 across both Android and iOS for non-gaming marketers.

When game marketing performance added in, Twitter jumped from 13th to the 8th highest ROI on iOS and from 18th to the 7th highest ROI.

Marketers also increased spending on Snapchat in 2017, with positive results. On iOS, Snapchat drove the sixth highest ROI for non-gaming marketers and the 15th highest ROI across all verticals. This revelation bodes well for Snapchat, which opened its marketing API to the masses just this week.

Video-focused media sources Vungle, Unity Ads and AdColony all moved to the top five on Android in 2017. This is the second year in a row that all three earned top spots for ROI, shining a light on the effectiveness of mobile video marketing. Each of the media sources also captured a greater share of marketing budgets on both platforms last year.

Despite launching less than two years ago, Apple Search Ads has delivered high ROI for iOS mobile marketers. It’s no wonder, then, that marketers poured more money into it last year. Apple Search Ads rose from twenty-third to sixth highest-volume media source on iOS based on total ad spend between 2016 and 2017.

Apple Search Ads drove the second highest return on iOS in 2017. The platform jumped six spots in the rankings, from the 10th highest return in 2016 to fourth highest in 2016 worldwide.