Researchers William Marmie and Alice Healy (2004) asked participants to study an unfamiliar coin for short periods of time, ranging from 15 seconds to 60 seconds. The results showed that participants were better able to remember details of the unfamiliar coin than the familiar U. S. penny. This finding confirmed that one of the most common reasons for forgetting is:

Mankiw attributes – chapter 1 and his 10 principles – differences in living standards within a countryover time and across countries at a moment in time to: a. the presence or absence of inflation and unemployment.b. the allocation of resources between private markets and the public sector.c. those that have dealt successfully with the efficiency v. equality tradeoff and those that haven’t.d. differences in productivity.e. ones that think at the margin and respond to incentives and those that don’t.