As Georgia considers legalizing Las Vegas-style casinos in the state, the threat that new casinos will steal gamblers from already established regional casinos is growing.

Georgia State Rep. Ron Stephens first introduced gambling legislation in the spring of 2015, which failed after opponents delayed the vote on the bill past the predetermined deadline in February 2016. Still, a recent Atlanta Journal Constitution poll showed that 56% of citizens in the state support legal gambling while 36% are opposed.

The trouble for investors in the gambling industry is that Georgia is surrounded by states that already have regional casinos, including Florida, North Carolina and Alabama, as well as other nearby states including Louisiana and Mississippi, raising the possibility that there won't be enough gamblers to go around.  Nationally, gambling revenue in the 23 states that allow casino gambling -- not counting states with only Native American casino gambling -- through November was $37.1 billion, up 0.9% through the first 11 months of the year, according to the UNLV Center for Gaming

"Cannibalization is a concern in regional gaming," Union Gaming analyst John DeCree told TheStreet in a recent interview. "Regionally, the market is stable, but it is not high growth." 

Though casino gambling revenue is on track to rise for the sixth consecutive year, not every state saw growth in 2016. The steepest decliners were New Mexico, down 9.85%, Louisiana, off 5.11% and West Virginia, which was down 3.75%. Overall nine states experienced revenue declines through November last year. 

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Eastern states such as Delaware, New Jersey and West Virginia have been affected by neighbors Pennsylvania and Maryland, which have only recently legalized casino gambling. Revenue in both Delaware and New Jersey fell less than 1 percent last year.

Pennsylvania and Maryland's gaming revenue through November was up 2.98% and 6.63% respectively in 2016. 

Penn National's (PENN) - Get Penn National Gaming, Inc. Report outlook, for instance, was lowered to "neutral" from "overweight" in a recent JPMorgan note. The firm believes that the opening of MGM Resorts International's (MGM) - Get MGM Resorts International (MGM) Report  $1.4 billion National Harbor resort in Maryland will take significant business from Penn's property in Charles Town, West Virginia, which lies within a few miles of the Maryland state line. Penn National rose 0.67% to $13.45 in Thursday trading, while MGM fell 1.38% to $28.63.

States often see casino gambling as an easy way to increase their tax base, but the long-term negative effects of gambling has split state legislatures across the country.

In Maryland, proponents of legalized casino gambling pointed out that the tax revenue would go to schools, and indeed casino taxes in Maryland have added hundreds of millions of dollars to the state's schools since table games were legalized in 2012. 

However, a new study from Central Atlanta Progress warned Georgia legislators that while legalized gambling would increase the state's tax base, the ill effects of problem gambling, crime, bankruptcy and political corruption outweighed those gains.