While Pew's surveys are some of the longest lasting in the industry, I'm always a bit skeptical about their numbers revealing some survey bias, at least compared to measured online usage stats.  Admittedly I'm a bit biased, but I think you'd find some similar demographic stats backed up by measured media usage in Nielsen's Social Media Report (full disclosure: my employer) http://blog.nielsen.com/nielsenwire/social/2012/  Of course these stats focus on online adults (and teens) in the US, but since online access is nearly universal by now I think they're just as representative of consumer's actual behavior using social media sites - for one, Tumblr usage is much more widespread, as I'd expect.

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