Former Vice President Joe Biden has aggressively invested on Facebook advertising since entering the presidential contest in late April, having spent more than $1 million on the social networking site and outpacing President Trump’s reelection campaign in three of the last four weeks.

But it’s not just spending for spending's sake. For Team Biden, there appears to be a decidedly straightforward strategy behind the ad investment: Facebook is increasingly a good place to reach older people, and older people are the ones who tend to vote.

According to the Democratic communications firm Bully Pulpit Interactive, which has been tracking Facebook spending for the candidates, an estimated 49.4 percent of the money Biden’s campaign has spent on Facebook has reached users between the ages of 45-64. An additional 32.7 percent has reached the 65 and older crowd. Just 17.4 percent has reached 25-44 year-olds. During that same time—March 30-May 18—President Trump’s campaign had 45.2 percent of their ads reach the 45-64 age demographic, with 27.9 percent for 65 and older and 22.1 percent for those between the ages of 25 and 44.

The data could be the result of older Biden and older Trump supporters being more engaged with the content the campaigns are offering. But experts say it’s likely not entirely coincidental.

“Age is a targeting setting the campaign has to choose when setting up ads,” Mike Schneider, a partner at BPI explained. “Of course, who is reached is somewhat based on Facebook’s user base—but safe to say major differences between campaigns are based on intentional decisions.”

The Biden campaign did not immediately respond to a request for comment about the tactics behind their Facebook ad purchasing.

That they would invest in trying to reach older audiences makes political sense. It’s the demographic that’s been pushing him to an early primary lead. In an early May poll of New Hampshire conducted by Monmouth University, Biden held a clear overall lead over his nearest competitor, Sen. Bernie Sanders (I-VT). But while he was trailing Sanders 27 percent to 20 percent among voters aged 18-49, he was beating him 36 percent to 19 percent among the 50-64 crowd, and crushing among the 65 and older crowd: 53 percent to 9 percent.

The Sanders camp has appeared to pursue almost the inverse model of Biden. According to the BPI analysis, from March 30-May 18, Sanders’ Facebook ads were seen 50.1 percent by voters aged 25-44, 25.7 percent by voters aged 45-64, and 12.7 percent voters by aged 65 and older.

Over that span of time, only a few candidates had their Facebook ads seen by a larger share of voters over the age of 65 than Biden, including Sen. Amy Klobuchar (D-MN), Sen. Michael Bennet (D-CO), and former Rep. John Delaney (D-MD). An estimated 39.1 percent of Klobuchar's ads were seen by that age demographic, though her campaign spent just a fraction of what Biden did. And for Delaney it was 40.4 percent, also with significantly less spending. An estimated 49.4 percent of Bennet’s ads reached that bracket.

According to the Pew Research Center, around 79 percent of those aged 18 to 29 use Facebook while only 46 percent among those aged 65 and older say they do. But the percentage of older users has more than doubled since August 2012, when 20 percent of people 65 and older said they used it.

While two septuagenarian candidates have led the early polling, the 2020 Democratic primary field is also stocked with younger candidates like former Texas Rep. Beto O’Rourke, South Bend Mayor Pete Buttigieg, and Rep. Tulsi Gabbard (D-HI). And the breakdown of their ad reach and spending on Facebook suggests that they, like Sanders, are aiming for a younger demographic.

According to BPI, 21.6 percent of Buttigieg’s ads in the aforementioned timeframe reached users ages 13-24, while 43.8 percent reached ages 25-44, and 24.9 reached ages 45-64. O’Rourke’s ads are more evenly distributed, with 32.9 percent reaching those aged 25-44, 31 percent reaching those aged 45-64, and 20.6 percent reaching those aged 65 and older. The candidate whose ads reached the youngest set of users, according to the data, is entrepreneur Andrew Yang, whose candidacy began as an online phenomenon. An estimated 29 percent of his ads reached users aged 13-24, with 52.8 percent reaching the 25-44 age bracket and only 15.3 percent reaching those between the ages of 45 and 64.