Year Lowest 20% of earners Middle 20% of earners Highest 20% of earners x^2 y^2 x*y
1977 12 000 54 200 122 500
144000000
15006250000
1978 11 800 54 000 126 400
139240000
15976960000
1979 13 100 54 200 121 100
171610000
14665210000
1980 13 700 55 700 123 200
187690000
15178240000
1981 14 600 54 700 123 200
213160000
15178240000
1982 14 300 51 600 122 300
204490000
14957290000


Have I done this graph correctly? or is x the year and then i made different chart for each of the earners as they would be rep by y?

or is it right to do the lowest rep by x and the highest represented by y?

Thanks in advance