LinkedIn remains the most broadly used social network among the Fortune 500, with 93% of the companies analyzed maintaining an account, per the latest annual analysis from the University of Massachusetts. This year Glassdoor was measured for the first time, with 87% of companies active on their Glassdoor profiles. Beyond those platforms, Twitter (78%), Facebook (74%) and YouTube (64%) rounded out the top 5, with each dropping slightly from last year in usage. Meanwhile Instagram is the fastest-growing platform, up from 9% with an active presence in 2013 to 33% this year. Read the rest at MarketingCharts.