It was a rare day Elon Musk didn’t Tweet in the past year. But among CEOs he remains an outlier.

A review of S&P 500 CEOs by Bloomberg shows that fewer than one fifth have Twitter handles associated with their job.

Twitter recently surveyed “influencers” on the platform and found that two thirds expect CEOs to be on Twitter.

In addition, 90% of those polled expect CEOs to voice positions on social issues of the day.

That isn’t happening yet, but its a good bet it will become more common.

(You can replicate my chart on Musk on the Bloomberg terminal running: {Tweets by Musk <go>}; save the search then run {NT <go>} and click on the Custom Searches option.)