Generational replacement is a theory proposed by Paul R. Abramson and Ronald Inglehart that attributes changes in values between young people and their elders to their different circumstances growing up. Because people's formative experiences in pre-adult years tend to shape them throughout later life, if the younger birth cohorts in a given society have experienced fundamentally different conditions than those that shaped older birth cohorts, one will find substantial and persisting differences between the basic values of older and younger generations. As the younger birth cohorts gradually replace the older ones over time, one will observe predictable changes in the values and behaviour of the population of that society as a whole.