Following are miscellaneous questions about the data:

1. Are the years Y1, Y2, Y3, and Y4 calendar years, or some other 12-month periods?

2. Are the years Y1, Y2, Y3, and Y4 consecutive 12-month periods?

3. It is curious that the Heritage Provider Network has about 500,000 patients, but only about 70,000 patients per year are included in the data files. Thus, it is possible that the data may be a biased subset of the total population. How were the patients in the data selected?

4.  What exactly is a "vendor"? Please give an example.

Thank you for your help.

Are these calendar years we're dealing with?

Per #1 below, I'd like confirmation on that.  If so, it does keep thigns easy--though, it would seem, not as valuable.

I'd be far more interested if someone leaving on February were coming back in the 12 months following that, then to know if they're coming back in the next calendar year--which is 10 months away at that point.

Still, for this competition, are Y1, Y2, Y3, and Y4 calendar years?

For all the talk of "years", I couldn't find anything that said "calendar".  Sorry if I just missed it.

Services rendered for PNEUM (includes influenza) peak at month 2 in each year, if the date field is corrected for bias. This suggests month 2 is February, meaning they are calendar years.