There's a nice straightforward question for a change. Thanks!
The Las Vegas Convention and Visitors Authority has been conducting the annual statistical surveys for donkeys years, so there's a consistent source of data to consult and compare against, although it takes them a while to process all the polls they conduct and crunch all the numbers, so the available stats always lag a year or so behind the current numbers.
According to the most recent LVCVA Las Vegas Visitor Profile Study available, in 2012 16 percent of visitors were first timers, a figure that has remained pretty consistent in recent years: It was the same in 2011 and 2008, with slight increases in 2009 (17 percent) and 2010 (18 percent).
When it comes to the numbers regarding how many of those newbies' primary reason for visiting was to gamble, this had dropped from 2 percent in 2008 to 1 percent in 2012.
Where the numbers have diverged much more significantly is when it comes to the proportion of repeat visitors whose primary purpose of coming to Vegas to gamble, a number that has been on a steady decline from the 2008 figure of 15 percent, down to 9 percent in 2012. It's a trend that mirrors the shift in mentality that's occurred over the past decade or so and the diversification of Las Vegas' entertainment base, with casino win no longer being the leading source of income for many properties, who now rely as much on income from their nightclubs, shopping malls, restaurants, and special events.