Figure 5 shows a plot of first differences in the log of monthly lightweight vehicle sales over the same period as in Problem 11. Has differencing the data made the resulting series, Δln (Salest) = ln (Salest) ˆ’ ln (Salest ˆ’1), covariance stationary?
FIGURE 5 Change in Natural Log of Lightweight Vehicle Sales

Transcribed Image Text:

0.15 0.10 0.05 0.00 -0.05 -0.10 -0.15 -0.20 1992 1993 1994 1995 1996 1997 1998 1999 2000 Year AIn (Millions of Units) (Annualized)