The title of the graph says it all for some companies. But it's not just an affluent target market that's important. It's showing up in Google search results as well.
Even if you're not a technical whiz, you've probably heard about disagreements between Google, Twitter and Facebook. Last I checked, the agreements Google had between Twitter and Facebook were no longer in place. So exactly how much of Twitter and Facebook's data stream makes it into Google's Search Results is unclear. At least, I haven't been able to figure it out.
But Google+ is obviously OWNED by Google. Of course the data shared there will be accessible to Google. That's important because the social shares on Google+ can affect the ranking of your content in search results. Technically, Facebook Likes and Twitter Tweets should affect ranking as well, but if that data isn't always accessible to Google...why take your chances? Anyone executing a long tail keyword research strategy is going to want to take advantage of the Google+ share capabilities.
Many websites already have share buttons for the major social networks. If you haven't already updated your website with a Google Share button, now would be the time. There's an affluent market out there you could be influencing with your content!