As with a lot of things it's not as simple as pointing your finger at one reason. Responsive Management is a polling company that does many polls for the outdoor industries. They conducted an exhaustive survey to determine the cause for the recent trends which were showing up on many state wildlife agency surveys. Their study can be found here. http://www.responsivemanagement.com/... and their overall report including figures from the census is here.
Top ten reasons below the blood trail.
1. Economy was down. Construction bottomed out. Carpenters and others had time to go hunting.
2. Rich people got richer and had more money to blow on hunting.
3. Groovy Foodies. Game meat is cool of late.
4 and 5 Programs from the State Agencies to recruit new hunters and retain old ones. Many programs to introduce new hunters to the sport and to make more access available for existing hunters
7. to 10. Returning military, women, lapsed hunters returning to the fold.
Some things I picked up browsing through the stats...and that first link has a hundred or so pages of data and analysis.... Hunting populations have remained about 14 million (good thing or tags would be even harder to get) since the late 50s even though the population has increased steeply since then. Percent of the population hunting has dipped from around 8% to around 5%. Montana's hunter population dropped by about 25% when wolves reached high population levels around 2001 or 02. At the same time Idaho's hunting population increased. Massachusetts should stick to vegetarianism. Retired people are the biggest demographic closely followed by construction workers. Bankers and landscapers don't hunt much.
Who cares? Why does this matter? Forgetting the billions spent on hotels, beer, and camo, more importantly is conservation. Not suing government agencies as the latest iteration of the word is used but cash dollars to hire biologists and wildlife officers. The majority of monies spent on sage grouse and wolverines comes from hunting licenses. When poachers are cutting out gallbladders and hacking off paws in California the wages of the good guys that bust them are paid by hunters.