The cost of tomatoes. Figure 10.14 is a line graph of the average cost of tomatoes each month from January 1997 to December 2007. These data, from the Bureau of Labor Statistics' monthly survey of retail prices, are the price in dollars and cents per pound.
(a) The graph shows strong seasonal variation. How is this visible in the graph? Why would you expect the price of tomatoes to show seasonal variation?
(b) What is the overall trend in tomato prices during this period, after we take account of the seasonal variation?
