Steve, It sounds like the ID statement is working like it should. Here's what it does. For every record in the summarized output, the ID variables should be copied from a single observation that went into computing that summary record. Which observation's ID statements get used? As you noted, there is an element of "maximum value" in making the selection. With a single ID variable, it is the maximum value. With 2 ID variables, it is the maximum value of the first variable, but not necessarily the maximum value of the second variable. Since the rule is to take both ID variables from a single observation, "maximum" means take the maximum value of the first ID variable. For all those observations having the maximum value of the first ID variable, take the maximum value of the second ID variable. The only choice you have is that you are allowed to switch to "minimum" instead of "maximum". But the basic rule stays in place: all ID variables come from a single observation that went into computing statistics for the summary row. Good luck.
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