Cass Sunstein's 2013 NYRB review concludes the Simon-Ehrlich wager tested neither man's actual thesis about population and resources

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Reviewing Paul Sabin's The Bet for The New York Review of Books, legal scholar Cass Sunstein argues the 1980-1990 Simon-Ehrlich wager settled far less than its public mythology suggests. The wager tracked the inflation-adjusted prices of five metals over a decade; Sunstein's objection is methodological, not partisan: "Commodity prices are highly volatile, and they are a poor proxy for the effects of population increases. Simon and Ehrlich both believed that their bet would be a good test of their competing views on population growth. But on that point, both of them were wrong." On Sunstein's reading, the 1980s commodity price decline reflected macroeconomic conditions (notably a recession) more than population dynamics in either direction, so Julian Simon's win proved less about resource scarcity under population growth than either side's public framing claimed.

This complicates a reading of the wager as a clean vindication of Simon's optimism, without contradicting the separate finding that Simon himself privately doubted the result reflected more than luck — Sunstein's argument and Simon's own letter converge on the same conclusion (the bet under-determines the underlying question) from different directions and apparently independently.