1) The following graph shows the progression of the GDP and the median household income in the USA (source: Wikipedia). FRED - (Real Gross Domestic Product/Total Households), 1984=100 Real Median Household Income in the United States, 1984=100 160 150 140 130 Index of (Bil. of Chn. 2009 $/Thous.) , Index 120 110 100 90 1985 1990 1995 2000 2005 2010 2015 a) Why is the household income in the country expressed with the median and not with the mean? b) Before 1990, GDP and median household income grew together. How do you interpret the increasing difference between both