This paper provides a working definition of what the middle-income trap is. It classifies 124 countries that have consistent data for 1950–2010. First, the paper defines four income groups of gross domestic product per capita in 1990 purchasing power parity dollars: low-income below $2,000; lower...

The literature on aggregation has shown that the conditions for successful aggregation of micro production functions into an aggregate production function are far too stringent to be believable (Fisher 1969, 1971). Despite this, aggregate production functions continue being used. The reason is...