Larry Summers sure has become controversial for the comments he made about women and science. I happened to come across another controversial statement he made quoted in the book Eco-Economy, this time about trying to educate every girl in the world currently not being educated.
Lawrence Summers estimated that an investment of $2.3 billion to educate girls in primary and secondary schools would yield 20% annually. Each additional year of female education reduces fertility by roughly 10%. It would take adding 25 million girls to current primary education at $938 million/year and 21 million girls to secondary school at $1.4 billion/year.
This IRR is much higher than the maximum of 6% governments are getting on the roughly $1 trillion they are planning to spend on new power generating plants.