Hi,
I have firm data with IPO. It looks like
year firmid IPO
1990 abc 1
1995 abc 1
1997 def 1
2000 def 1
2000 ghi 1
2002 jkl 1
I want to calculate the years between IPOs if a firm has more than 1 IPO.
For example,
year firmid IPO duration
1990 abc 1 0
1995 abc 1 5 (1995-1990)
1997 def 1 0
2000 def 1 3 (2000-1997)
2000 ghi 1 0
2002 jkl 1 0
Thank you for your help in advance.