Textbook stuff on exit, entry and shutdown decisions:

Gas rigs have been disappearing particularly fast since late October, the last time prices were above $4.

Essentially, gas is so cheap that it’s no longer profitable to drill.

“Producers typically need $5 [per 1,000 cubic feet] to break even,” says David Greely, an energy analyst atGoldman Sachs (GS). The industry hasn’t seen prices consistently over $5 since September 2010, back when there were nearly 1,000 rigs operating in the U.S. The number of gas rigs peaked near 1,600 in mid-2008, when prices peaked at $10. (The boom was effectively confirmed in June 2009, when a Colorado School of Mines report showed that U.S. natural gas reserves were 35 percent higher than previously estimated.)

Other analysts say $5 is too high and that the average gas producer can still make money with the price between $3 and $4, depending on the well because different types of wells have different cost structures. Newer, high-production wells can turn a profit even with prices below $2, while older wells that are just trickling out gas need much higher prices to make money. That’s probably why there’s been stronger demand for horizontal rigs that specialize in fracking. Even those numbers have started to diminish in the last couple weeks.

Hat Tip: Jonathan Schultz, Kellogg MBA student