Latest statistics about the popularity of birding in the US show that it has grown significantly in the last 10 years.
Figures from the Forest Service's National Survey on Recreation and the Environment (NSRE) have been released and once again they show an upward trend in the numbers of people watching birds in the US. The latest NSRE results for 2004-2006 estimates that bird watching involves 81.4 million participants. This includes anyone who looks at birds while outdoors, rather than people who actively go out birding. The survey also assessed the actual number of days spent birding during a year which stands at an incredible 8.2 billion! In 1994-95 the figures were 54.4 million participants and 4.8 billion annual birding days.
More information about NSRE can be found here