Google does not provide detailed figures for YouTube's running costs, and YouTube's revenues in 2007 were noted as "not material" in a regulatory filing. In June 2008, a Forbes magazine article projected the 2008 revenue at $200 million, noting progress in advertising sales. In January 2012, it was estimated that visitors to YouTube spent an average of 15 minutes a day on the site, in contrast to the four or five hours a day spent by a typical U.S. citizen watching television. In 2012, YouTube's revenue from its ads program was estimated at <answer>3.7 billion</answer>. In 2013 it nearly doubled and estimated to hit 5.6 billion dollars according to eMarketer, others estimated 4.7 billion,
What was youtube's estimated ads revenue in 2013?
3.7 billion