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statisticsstataeconomics

Stata: How to find firms which changed the status in the time-series dataset

I have a data set containing information about different firms' performance in time. It has variables: firm id, year, firm's exporting status (basically, 1 if it is exporter). I want to know how many companies (in a specific group, during specific time interval) made a exporting decision, e.g. changed exporting status from 0 to 1. I would like to avoid brute force approach by conversion to csv and then parsing by python script.

Solution

  • Here's one way that uses lag operators:

    clear

input firm_id   t   exp
0   1   0
0   2   1
1   1   0
1   2   1
1   3   1
2   1   0
2   2   1
2   3   0
3   1   1
3   2   1
4   1   0
4   2   0
end

xtset firm_id t
gen start_exp = cond(exp==1 & L.exp==0,1,0)
bys t: sum start_exp