Hi! I have a panel data with prices (p) item and time(t). I would like to compute the cumulative inflation. I.e.:
t p item p/p[t-1]
1 10 apple .
2 12 apple 1.2
3 10 apple 0.833
4 15 apple 1.5
1 20 orange .
3 21 orange 1.05
4 20 orange 0.952
5 20 orange 1
6 20 orange 1
that implies for apples the cumulative inflation was: 1.2 for t=2, 1 for t=3 and 1.5 for t=4 and for oranges: 1.05 for t=3 and then 1 until the end of the period. How can I compute that with stata.

For the last column (the monthly inflation) I have:

Code:
gen price_change_per = price/price[_n-1] if item==item[_n-1]
but I cannot come up with the doce for the cumulative one? I'm concerned not only for the final value of the cumulative inflation (1.5 for apples and 1 for oranges) but also for the evolution it has.

Best and thanks a lot!