The concept of development was defined in the 1950s and 1960s as a largely economic process, in which wealth would trickle down and improve human welfare. Today this has now given way to much broader definitions of development. UNDP has focused on human development and issued a series of Human Development Reports exploring critical issues such as gender inequality, growth, poverty and consumption patterns (UNDP 1998 and previous years). It also calculates a human development index based on life expectancy, adult literacy, school enrolment and GDP per capita.