A time-series plot often helps you to determine the appropriate model to use. For this problem, use each of the time-series presented in the following table.

a. Plot the observed data (Y ) over time (X ), and plot the logarithm of the observed data (log Y ) over time (X ), to determine whether a linear trend model or an exponential trend model is more appropriate. (Hint: If the plot of log Y versus X appears to be linear, an exponential trend model provides an appropriate fit.)

b. Calculate the appropriate forecasting equation.

c. Forecast the value for 2006.