The catastrophe unfolding in the Gulf of Mexico has been portrayed as a one-of-a-kind disaster, a perfect storm of bad equipment, bad planning and bad luck.

But it’s far from the only spill that’s taken place this year – or even the only spill occurring in the Gulf right now.

On June 7, the Mobile Press-Register reported that the Ocean Saratoga rig has been leaking into the Gulf since April 30. Interior Department spokeswoman Kendra Barkoff confirmed the next day that “small amounts of oil” were leaking from the wells beneath the rig, about 10 miles from Louisiana’s southeastern coast.

Taylor Energy, the well’s owner, said in a statement that it was engaged in an “ongoing well intervention plan” with the government to fix damage caused by Hurricane Ivan in 2004, and that no significant new spill had occurred.

The Deepwater Horizon isn’t the only recent spill for BP, either. On May 25, according to Reuters, an accident on the Trans-Alaska pipeline spilled thousands of barrels of oil and forced the pipeline to be shut down for more than three days. BP is the largest owner of the pipeline operator, controlling 47 percent. (Read our story about BP’s troubled history in Alaska and its other U.S. operations.)

In addition, there was the Jan. 24 spill in Port Arthur, Texas, when an Exxon-Mobil tanker collided with an outgoing vessel and dumped nearly half a million gallons of oil into the Gulf.

If it seems as if oil spills – and particularly offshore spills in U.S. waters – are on the rise, that’s because they are.

A USA Today analysis of federal data found that spills from offshore oil rigs and pipelines have more than quadrupled in the last decade. From the 1970s to 1990s, offshore facilities averaged four spills per year of more than 50 barrels. From 2000 to 2009, the annual average soared to 17.

The report also found that the rate of oil being spilled was increasing faster than the growth in production. From USA Today:

In the 1980s, an average of about 2,900 barrels of oil and other toxic chemicals spilled a year. That figure rose to more than 4,400 in the 1990s and to more than 6,100 in the 2000s. Offshore oil production increased during that time, but the rate of barrels spilled per barrels produced continued to increase.

The company with the most spills in the last decade was BP, which had reported 23 spills of over 50 barrels without counting the Deepwater Horizon blowout.

Why are offshore oil facilities spilling more in recent years than they have in the past?

One possibility is that regulators haven’t been able to keep up with the surge in offshore drilling. The Washington Post reported Thursday morning that the Minerals Management Service has only seven more inspectors now that it did in 1985, even as offshore drilling projects have skyrocketed. From the Post:

Although the number of exploration rigs soared and the number of deep-water oil-producing projects grew more than tenfold from 1988 to 2008, the number of federal inspectors working for the Minerals Management Service has increased only 13 percent since 1985.

A message left for MMS this morning has not been returned.

Stefan Mrozewski, a drilling engineer with Columbia University’s Borehole Research Group and a former oil industry employee who once worked on the Deepwater Horizon, said the increase may in fact be driven by a very different dynamic – better voluntary reporting of spills by the industry.

Oil companies and service companies in the Gulf of Mexico “have – at least over the past 10 years – been extremely conscientious about report [sic] spills, incidents, hazards, etc,” wrote Mrozewski in an e-mail. “I would venture that the same attitude did not prevail in the 90s, and certainly not in the 70s.”

David Miller of the American Petroleum Institute, a trade association for the oil and gas industry, said that offshore drilling was heavily regulated by the government, citing the MMS’s extensive guidelines for deepwater drilling.

“There’s quite a few regulations that the industry has to follow to be in compliance with the MMS,” said Miller.

Another possibility is that oil is simply harder to reach now – that increased consumption has led companies to turn to deeper waters and riskier procedures to satisfy the ever-expanding demand for energy.

“While the point of “peak oil” may or may not have been reached, what Michael Klare, a professor at Hampshire College, has dubbed the Age of Tough Oil has clearly begun,” wrote the New Yorker’s Elizabeth Kolbert on May 31.