Facebook-owned Instagram grew its reach 5.3 percentage points in the last year. Source: Facebook

Over the last few years, the biggest trend in technology has been the steady shift toward mobile. Led by the tremendous smartphone boom in both India and China, survey firm StatCounter estimated 43.3% of all web pages browsed in Asia were from mobile phones last year, up from 4.5% in 2010. For many in developing markets, smartphones have supplanted desktop computers as the primary computing and Internet device.

Mobile has exploded in developed markets as well, as apps have increased the convenience factor of on-the-go browsing. Both Apple's iOS and Alphabet's (NASDAQ:GOOG) (NASDAQ:GOOGL) Android host in excess of 1 million apps providing smartphone users with a plethora of games, media, news, and social networking options. Last year, studies from both Forrester Research and Nielsen showed most U.S. smartphone owners only use a tiny fraction of their apps -- Nielsen found most users only use 26 or 27 apps a month, while Forrester reporting 84% of time is spent on just five apps.

The reason why is that while the number of apps available has increased, on-device storage hasn't grown as much. This creates urgent battles among  companies to convince users to download their apps onto our devices.

It appears that in that download war between Alphabet and Facebook (NASDAQ:FB) in the U.S. market, Facebook is winning.

Large reach growth for Facebook 
According to comScore's monthly Mobile Metrix survey for January 2016, Facebook and Facebook Messenger were the No. 1 and No. 2 top smartphone apps with a reach percentage of 78.4% and 64.1%, respectively. Additionally, its Instagram app was No. 9, with a 39% reach. More impressive than placing three apps in the top 10 was the year-over-year growth for these apps.

Current PositionAppJan '16Jan '15YoY Growth (%p)
1     Facebook 78.40% 69.7% 8.7
2     Facebook Messenger 64.10% 47.4% 16.7
3     YouTube 61.10% 54.5% 6.6
4     Google Play 51.00% 51.8% (0.8)
5     Google Search 50.20% 51.5% (1.3)
6     Google Maps 48.70% 43.2% 5.5
7     Gmail 44.80% 42.1% 2.7
8     Pandora Radio 43.30% 42.5% 0.8
9     Instagram 39.00% 33.7% 5.3
10     Amazon Mobile 33.40% 24.4% 9.0

Source: comscore. Bold rows highlight a Facebook or Alphabet-owned app.

Zuckerberg took a chance when he sliced instant messaging out of the main Facebook app and forced users to download the Messenger app separately, but the service has jumped from 16.7 percentage points during the last year, leading the top 10 apps in percentage-point growth. Perhaps just as impressive, Facebook was able to grow the already large footprint of its eponymous app 8.7 percentage points; now, nearly 4 out of 5 U.S. smartphones have the app downloaded. Additionally, Instagram added 5.3 percentage points of year-on-year growth.

Alphabet's reach growth has been slower
Compared to Facebook's average year-on-year growth of 10.2 percentage points, Alphabet's reach growth was noticeably slower. Across Alphabet's five top-ten apps, two actually reported reduced reach this year (Google Play and Google Search) and the average growth across all apps was a scant 2.5 percentage points. 

One potential explanation for Alphabet's slow reach growth is that the Android operating system last market share to iOS during the year. In January 2015, 53.2% of all smartphones in the United States were Android. That fell to 52.8% in January 2016. Apple's native apps perform many of the functions Alphabet's apps do, mitigating the need for an outside app.

Facebook really doesn't have developed competitors for its main site, nor for  photo-sharing service Instagram. Google attempted to take on Facebook with Google+, but the company has recently deemphasized the service. Look for Facebook to continue to improve its mobile-app reach, but Alphabet's host of services to continue to enrich investors as the shift toward mobile continues.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.