But at least nine people were asphyxiated, burned or fell to their deaths at U.S. refineries during those years, according to a Houston Chronicle review of media accounts, industry statistics and fatal accident reports to OSHA.

Twenty more have died since then — 15 in a March 23 BP Texas City accident alone.

How do the refinery dead disappear? The answer is fairly simple.

Increasingly, the accuracy of government safety statistics is undermined by the changing work force, according to the Chronicle. These days, up to half of refinery workers are contractors, who generally get some of the most dangerous jobs.

Since these employees do not work directly for petroleum companies — even though some toil for years at the same refinery — their deaths get diverted to several catch-all construction or maintenance categories, such as "1799, Special Trade Contractors, Not Elsewhere Classified."

"They'll show up in the statistics but not as refinery workers," explained retired Bureau of Labor Statistics (BLS) economist Guy Toscano. "The more dangerous an occupation, the less likely a company would want to hire those people directly — they want to boost their own safety rates and decrease their liability."

Nor are such deaths generally counted in the refineries' individual injury and accident logs, which OSHA uses to determine its "hit lists" of dangerous facilities targeted for more frequent inspections. The way U.S. safety statistics are kept, a work site will not generally get a black mark if contractors from other companies are killed or injured there — only if a permanent employee dies or gets hurt.

Without contractor fatality and injury data, OSHA inspectors may not pick up a problem refinery, said former OSHA Administrator Patrick Tyson, now a safety consultant with the Atlanta firm of Constangy Brooks & Smith.

"If the site gets picked up, it's going to be almost a fluke," Tyson told the Chronicle.

John Miles, the OSHA administrator for the five-state region that includes Texas, agreed in an interview with the Chronicle that reporting which emphasizes the employer over the site of an accident can affect OSHA's ability to both find and target dangerous businesses in some cases.

Miles added that currently no one is pushing for reforms in the reporting system.