While the illustration may have moved some investors from zero to a token weight in foreign, many investors and advisors fixed on the optimum point at 20 to 30 percent as a maximum foreign weighting.

FORBES: How Much International?

Earlier work by Dr Schlenker has showed that plants have skewed preferences: they dislike temperatures beyond the optimum more than they dislike temperatures below the optimum, so increasing warmth can have worsening effects beyond a certain point.

ECONOMIST: Climate change and crops