The Y - Axis on this graph is the Civilian Unemployment rate. This axis shows the percentage of people who are in the labor force who do not have jobs. During recessions, the unemployment rate rises because there are less jobs available to people because there are less goods being produced in the economy. The unemployment rate decreases during growth period because there are more goods being produced in the economy and thus more labor is needed to produce these goods. The highest unemployment rate was in the 80s because the government made an active attempt to stop stagflation during that period. However, in order to do that, they intentionally slowed the economy and thus increased unemployment rates to very high rates. The lowest unemployment rate was around the 40s during the second world war. This was because the government had to employ large quantities of people to work in military industries. This was a very low rate and was achieved because the government had to take control of the economy during the war.