I've been looking all around, asking around, etc, and I can't seem to find
out how to create new observations within my dataset.
Here are the specifics of my problem:
I have counts of cases by zip code and year (one observation with count for
each zip, and year). It happened that I ended up with "missing"
observations if the count of cases was zero in a year, so my data look
something like this
zip year count
06010 1986 1
06010 1987 2
06010 1988 2
06010 1990 7
...
How would I create a new observation for this zipcode in 1989 that has a
count of 0? I need to be able to create some lagged variables by year and zip.
