Five years ago, Matthew R. Simmons and I bet $5,000. It was a wager about the future of energy supplies  a Malthusian pessimist versus a Cornucopian optimist  and now the day of reckoning is nigh: Jan. 1, 2011.

The bet was occasioned by a cover article in August 2005 in The New York Times Magazine titled “The Breaking Point.” It featured predictions of soaring oil prices from Mr. Simmons, who was a member of the Council on Foreign Relations, the head of a Houston investment bank specializing in the energy industry, and the author of “Twilight in the Desert: The Coming Saudi Oil Shock and the World Economy.”

I called Mr. Simmons to discuss a bet. To his credit  and unlike some other Malthusians  he was eager to back his predictions with cash. He expected the price of oil, then about $65 a barrel, to more than triple in the next five years, even after adjusting for inflation. He offered to bet $5,000 that the average price of oil over the course of 2010 would be at least $200 a barrel in 2005 dollars.

I took him up on it, not because I knew much about Saudi oil production or the other “peak oil” arguments that global production was headed downward. I was just following a rule learned from a mentor and a friend, the economist Julian L. Simon.