calculating how percentiles performed in a panel dataset

Dear Statalist,

My panel dataset is as follows

year firm size sales

2000 firm1 size1 sales1
2000 firm2 size2 sales2
...
2001
2001
...

2020

There are about 200/300 firs in each year.
I want to calculate the mean sales for each year for each percentile (top 25%, 25%-50%,50%-75%,75%-100%) under four
variables based on the size of the firms. For example in the year 2000, top 25% largest firms what were the sales, same year next 25%-50% what were the sales etc.
I use them to time series plots and for tables.
Appreciate your help.