st: Getting different vertical lines in each graph produced by xtline

[David Merriman <dmerrim@gmail.com>]

I have a panel data set of states over 25 years of so with their
corporate income tax revenue.

I have produced 50 graphs using xtline showing the change in corporate
income tax revenue by year using sytax like

xtline  corp_y_index

Many states have over the course of this period adopted a policy that
may have changed the growth rate of corporate income tax revenue.
I have a variable named d_payroll_app  that equals either zero or 1 in
each year in each state.  A 1 indicates a policy change.

I would like to add a vertical line to each graph in each year in
which d_payroll_app=1.

I thing that I could do something like this manually using syntax like

graph line corp_y_index year if state==1, xline(1985) name(graph1)
graph line corp_y_index year if state==2, xline(1987) name(graph2)
.
.
.
graph combine graph1 graph2.....

This would be tedious and would require that I look up each year in
which each state had a policy change.

Is there an easier way to do this?

Thanks


David Merriman
dmerrim@gmail.com
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