They found many non-obvious factors which correlate to strong sales performance and have now changed their screening criteria and raised first-year productivity by over 20%.
Mr Greenspan is placing a lot of weight on the recent increase in America's productivity growth, which has helped offset faster wage growth, and may well have raised the economy's long-term growth rate.
On a return trip to Rwanda last week, we saw ample evidence in Kigali: a new and fully-leased 20-story skyscraper, tower cranes that punctuate the skyline, and shiny metal roofs in rural areas that attest to growing household income. (Rwanda raised one million people out of poverty between 2006 and 2011.) Agricultural cooperatives improve efficiency and productivity.