DF = data.frame(
    year=1989:2007,
    global_rock=c( 15.32, 1.62, 28.43, 11.91, 20.71, -2.15, 23.29, 15.96, 11.12, 0.37,
                   27.43, 8.57, 1.88, -7.96, 35.98, 14.27, 10.33, 15.94, 16.71 ),
    lipper=c( 14.76, -1.91, 20.67, 6.18, 22.97, -2.44, 20.26, 14.79, 14.27, 6.25,
              34.44, 1.13, -3.24, -8.11, 32.57, 15.37, 11.25, 12.70, 9.65 )
)