“Too many barns and not enough horses” is basically how the major-league arena landscape in the New York City area shapes up:

Five major complexes — four existing and one planned — will soon be slugging it out within an area 30 miles wide.

At least two of the existing arenas already lose money, and experts say further casualties are almost guaranteed.

“Five arenas is not going to work,” said Mark S. Rosentraub, a professor of sports management at the University of Michigan. “I don’t think four works, even in a market as large as New York. There’s competition in every direction and there aren’t enough events.”

The five arenas in question all have their own issues:

In Brooklyn, the developer Bruce C. Ratner is racing to start construction of a $772 million arena for the Nets basketball team, even as Newark woos the Nets for its money-losing Prudential Center arena.

In New Jersey, the owner of the Devils hockey team, which abandoned the Izod Center in the Meadowlands to play at Prudential Center, wants Gov. Jon S. Corzine to tear down the Izod Center, in the hopes of eliminating a competing venue.

On Long Island, Charles Wang is pressuring local officials to approve his plans to rebuild the much-maligned Nassau Coliseum for his Islanders hockey team by hinting that the team might flee to Queens, or leave New York altogether.

Then there is Madison Square Garden, whose owners are starting a $500 million overhaul of the 41-year-old arena. The Garden’s cachet helps draw performers, but the arena has another considerable advantage: three major professional sports teams play there, leaving the Garden with fewer dates to fill than the region’s other arenas, which all play host to only one major sports team apiece.

This doesn’t even count the other large-scale stadia in the same neighborhood: Giants Stadium, Yankees Stadium, and Citi Field. They’re slightly different animals, in that only a very select few musical acts perform mega-stadium shows these days. Still, they provide an x-factor in the competition over non-music venues.

I’m not sure just how dire the situation is. For one, the Brooklyn arena situation is pretty close to collapsing. So I wouldn’t count on those seats even being built. From there, the Nets will have little choice but to move to Newark and rejoin the Devils as co-tenants in the same arena, thus filling out the Prudential Center’s dates. (The final domino to fall in that scenario is the eventual demolition of the Izod Center, which would be without a primary tenant.)

The rule of thumb about an arena needing 200 booked dates to generate an operating surplus is telling. It means that the trend toward major-league sports teams demanding their own, exclusive barn (especially in the Sunbelt) benefits nobody but that team and its owner. The facility itself suffers from lack of use, which prompts demands for subsidies (zero rent, cash infusions, operating concessions, etc.) from the host city/county/state. And, of course, a glut of sports/entertainment seats without enough butts to fill them year-round. It’s a situation that screams for macro-economic oversight.