CEOs at America’s 500 highest-grossing companies have been slow to embrace social media, despite the proven effective it can have for businesses.

A study by CEO.com and Domo, a business software company, found that just 32% of top CEOs have at least one account on a social network.

The study did find however, that CEOs are most active on LinkedIn, with 27.9% having accounts with the business-focused social networking site, compared to 25.9% in 2012. According to a study by Pew Internet, 20% of the US population is on LinkedIn.

Among the CEOs who have LinkedIn profiles, just 25 of them have more than 500 connections. Hewlett-Packard CEO Met Whitman has 265,852 connections on LinkedIn, but Alan Mullaly, CEO of Ford Motor Company does not have a LinkedIn profile.

Twitter has far fewer CEO users, with just 5.6% from the top 500 companies, compared to just 3.6% last year. Among online adults in the US, 18% are on Twitter, according to Pew.

Of the CEOs on Twitter, only 19 are "active," according to the study, meaning they tweeted in the 100 days prior to the study. The active CEOs tweet, on average, only once a day.

Warren Buffett has only tweeted twice since May 2, but he already has 542,000 followers. The first tweet simply said "Warren is in the house." The second tweet promoted one of his essays on how women can help America to prosper.

The number of CEOs on Facebook stands at 7%, relatively unchanged from 7.6% last year. According to Pew, 67% of online adults use Facebook, a significantly higher proportion.

Not surprisingly, the most popular CEO on social media is Mark Zuckerberg, with 18,764,161 followers.