10.15 The cost of imported oranges. Figure 10.15 is a line graph of the average cost of imported oranges each month from July 1995 to April 2012. These data are the price in U.S. dollars per metric ton.
(a) The graph shows strong seasonal variation. How is this visible in the graph? Why would you expect the price of oranges to show seasonal variation?
(b) What is the overall trend in orange prices during this period, after we take account of the seasonal variation?