Atlantic City has lost more than half of its casino revenue during the past nine years.

That depressing news Wednesday came only hours after New Jersey lawmakers introduced a bill that has long been the worst nightmare of the Atlantic City casino industry — a referendum to expand casino gambling to the northern part of the state.

Moody's Investors Service immediately cautioned that any more casinos in New Jersey would be "particularly bad news for the already struggling Atlantic City gaming market."

"In our view, the additional competition will likely cause more casinos to close," the Moody's report said, adding that could occur both before and after a northern New Jersey casino opens.

Figures released by the state Division of Gaming Enforcement show that the city's eight casinos took in $2.56 billion in 2015 — a 6.5 percent decline from 2014.

It's also less than half of what Atlantic City's casinos took in during their best year, 2006, when annual revenue was $5.2 billion.

But when only the eight currently operating casinos are included in the comparison, 2015 revenue was actually up by 3.1 percent compared with 2014. Twelve casinos were operating at the start of that year, but four — The Atlantic Club, Showboat, Revel and Trump Plaza — shut down in 2014.

Mayor Don Guardian, whose city has struggled mightily since the downturn began nine years ago, was hopeful the surviving gambling halls have stabilized. But he said the long-term harm has been unmistakable in lost money and jobs.

"We had a monopoly and 12 casinos," he said. "Now there are 30-something casinos in the northeast, and we're about to have gambling in the northern part of the state. There are more gambling places than there are gamblers willing to gamble."

Guardian also has been forced this week to respond to an attempt by the state to takeover the city's finances. New Jersey Senate President Steve Sweeney introduced a bill Tuesday that would give the state vast power over most major decisions, including the right to sell off city assets and land.

The year-end casino figures for 2015 show five of the eight casinos won more that year than the year before. The largest percentage increase was logged by the Golden Nugget, which was up 24.6 percent for the year to $231.2 million. The biggest decline was at the struggling Trump Taj Mahal, which was down 16.5 percent to $180.2 million.

Internet gambling showed a healthy 21.2 percent increase in New Jersey in 2015, rising in its second full year to nearly $149 million.

The monthly figures for December show the casinos' collective revenue up less than 1 percent compared to December 2014.

Sweeney introduced a bill late Tuesday that would authorize a referendum on two new casinos in the northern part of the state. Although it does not specify locations, the leading candidates are the Meadowlands sports complex in East Rutherford, and in Jersey City.

The bill would send half of the gambling tax revenue to help redevelop Atlantic City.

A state Senate committee will consider the bill Thursday.

Expanding casinos to northern New Jersey is sure to further hurt an already damaged Atlantic City market. In 2006, when the first casino opened in neighboring Pennsylvania, Atlantic City's casinos won $5.2 billion. Ever-increasing competition in neighboring states is the largest single reason for the decline.