FYI: My ratio calculation seems to work when applied within the first 24 hours of a meme. If a meme receives 20% upvotes in the first 4 hours of being featured and after the first 4 hours, if it maintains at least 10% - it's going to make it to the front page of the politics stream.
Most of the memes this lib submitted to the politics stream haven't managed to accumulate 1% upvotes in 9 months.... They didn't come anywhere near the front page of the stream, which is how I gauge meme success in the politics stream.