Aug. 25 (Bloomberg) -- Crude oil has become so expensive compared with natural gas that the record price ratio between them probably won’t last, analysts say.

The CHART OF THE DAY shows the prices of these commodities since 1990, when natural-gas futures started trading on the New York Mercantile Exchange, in the top panel. The ratio between them, which closed at a record 26.4-to-1 last week, appears in the bottom panel.

The ratio has more than tripled this year amid a 67 percent increase in crude prices, bolstered by speculation that Chinese demand will climb. Gas prices have fallen 48 percent on reduced demand from industrial companies and the start of production at new U.S. fields.

“History clearly suggests that the price gap will eventually narrow, through some combination of oil prices falling and natural-gas prices rising,” Donald Marron, a former member of the Council of Economic Advisers, wrote in an Aug. 21 posting on his blog.

The timing of any return to historical norms, also known as mean reversion, is questionable. Marron didn’t speculate in his posting about when that might take place.

“Who knows when we’ll see some reversion to the mean,” analysts at Bespoke Investment Group wrote yesterday in a comment highlighting the oil-gas ratio.

(To save a copy of the chart, click here.)

To contact the reporter on this story: David Wilson in New York at dwilson@bloomberg.net

Last Updated: August 25, 2009 11:35 EDT