YouTube is bigger and growing faster than previously thought, according to a new report. Estimates released Wednesday by research firm eMarketer peg revenue for Google’s video site at $5.6 billion this year, up 51% from $3.7 billion in 2012. That’s significantly faster growth than estimated by Mark Mahaney of RBC Capital Markets, who thinks YouTube revenue will grow 32% to $4.7 billion this year. Google doesn’t disclose financial information for YouTube. If eMarketer is correct, YouTube would be about nine times the size of Twitter, as measured by revenue. Analysts expect Twitter will post revenue of $640 million this year. Twitter is valued at $29 billion, suggesting that YouTube significantly boosts Google’s value. There’s a caveat, however. EMarketer measured YouTube’s gross revenue, the amount Google takes in from advertisers before paying a cut to certain content providers.