Calculate entry-exit rates of firms in a sector in various years.

[Demet Korkut]

Hi,
I want to calculate entry-exit rates of firms within a sector in a range of years. I added the sample data set below. There are some challenges in the data which hindered me to calculate the relevant rates with simple codes (creating dummies for entry and exit year etc.). First is some firms exit in year 2011 and enter in 2012 again. The second is they may be active before 2010 and after 2012. So, these dataset only covers some part of the population. Therefore, the first year "2010" does not imply the entrance year for all firms.

* Example generated by -dataex-. To install: ssc install dataex
clear
input str1 firm int year
"a" 2010
"b" 2010
"c" 2010
"d" 2010
"e" 2010
"f" 2010
"g" 2010
"a" 2011
"b" 2011
"g" 2011
"d" 2011
"h" 2011
"j" 2011
"k" 2011
"k" 2012
"a" 2012
"b" 2012
"d" 2012
"e" 2012
"u" 2012
"v" 2012
"c" 2012
end

Thank you so much for your answers in advance.

Demet Korkut