- *I have a dataset, each firm each year has some application number. I want to know whether each year has add or drop application number.
firm frimID Application year
A 123 a 2013
A 123 b 2013
A 123 b 2014 A 123 c 2014 A 123 c 2015 B 456 e 2013 B 456 f 2013 B 456 e 2014 B 456 g 2015 here, for firm A, 2014 keep "b" drop "a" but add "c",2015 keep "c" drop "a" and "b" for frim B, 2014 keep "e", drop "f", 2015 drop "e" and "f", but add"g". I want to know all these changes per firm per year, count the number, how many dropped how many added. Thank you
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data procfessing how to know the changes per year, whether has observation names add or drop each year
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