Hi Forum,

I have been trying to do this on my own but I cannot find information either solve it. So I am hoping some of you could help me


So, I have a panel data, with monthly data for each id. However, many ids that I have appears more frequently in one year than in the other, and I believe this can harm my research.
Here is what I mean:


group(prod |
uct_type1 |
quantity | year
category) | 2013 2014 | Total
-----------+----------------------+----------
1 | 1 1 | 2
2 | 1 1 | 2
3 | 36 36 | 72
4 | 72 82 | 154
5 | 38 58 | 96
6 | 8 12 | 20


I wish, for instance, that for id==4, I have both years the same number of observations, so I am certain that the variable price (that I am interested) increase or decrease because of its changes and not because a year had more obs than the other.

Does anybody know how can approach this issue?

If you need any information, please let me know.

Thank you!!

Greetings,


Lena TF