In reply to Charles.

For time series, there are about a half dozen commonly used aspect ratios. They are discussed in the article "Banking to 45 degrees: Aspect ratios for time series plots." At the end of the program for that article, there is a little macro that you can use. However, SAS doesn't do this automatically since there is no agreement on the best aspect ratio to use for time series. For scatter plots, ASPECT=1 results in a graph that preserves the aspect ratio of the data.