In May, one of the broadest commodities indexes—the S&P GSCI—produced its biggest one-month gain since Iraq invaded Kuwait in September 1990.

The S&P GSCI increased 19.67% in the month. That compared to a gain of 22.94% in September 1990, according to Standard & Poor's, which released the results on Tuesday. (See table below.)

"Solid commodity gains in May were attributed to most commodities accelerating the recovery process from the sharp declines experienced during the second half of 2008 and first quarter of 2009," said Michael McGlone, S&P's director of commodity indexing in a statement.

Year-to-date through May, the S&P GSCI had registered a total return of 5.95%, led by strength in the energy and agriculture sectors.

Sparked by price increases in unleaded gas and crude oil, the S&P GSCI Energy Index increased 25.44% on the month for a year-to-date gain through May of 4.38%. The S&P GSCI Agriculture Index was the second-best-sector performer last month, increasing 12.37% for a year-to-date gain of 8.18% heading into June.

Metals also performed well in May. The S&P GSCI Precious Metals Index gained 11.41%, putting it up 12.71% for the year. The S&P GSCI Industrial Metals Index increased a more modest 5.82% on the month. But it has been the strongest year-to-date sector performer with a gain of 22.23% (led by a 55.72% increase in copper) through May.

--- This article was submitted by IndexUniverse's Murray Coleman.