C-SPAN's Biased Too?

I found this interesting: The Center for Economic and Policy Research finds that 51% of C-SPAN's coverage goes to conservative think-tanks, while only 23% goes to progressive or liberal think tanks. Perhaps this is just part of the overall trend that more conservative outlooks economics (and politics) seem to be "mainstream". To be honest, in my own limited viewing of C-SPAN, I've never noticed any sort of bias. Further, I don't really know anyone else that watches C-SPAN ever, so I'm not really sure how much it matters. Nevertheless, closer-to-heterodox think-tanks like the Economic Policy Institute or CEPR probably receive little to know play on this network or on any, and that only furthers the dominance of the mainstream, even if the so-called mainstream is not really an academic consensus.