firm age

[Mariam Al Sabah]

Hello,

I have 26,000 observations. I would like to calculate the age of these incorporations. What should I do? I am quite new to all this. The "Date of incorporation" is listed as a string value and looks like this;

31/12/1997
31/12/2000
31/12/2004
31/12/2012

Thank you.

[Rich Goldstein]

help datetime will get you started; for example:

gen int newdate = daily(oldvar,"DMY")
format newdate %td

you don't say when you want the age calculated to but you can then just subtract the newdate from the "goal" date; e.g.,

gen age=td(31dec2018) - newdate

which will give you age in days

my "newdate" and "oldvar" should, of course, be changed to whatever you want (or is already in your data)

[Mariam Al Sabah]

Thank you Rich! Worked great!

[Mariam Al Sabah]

I have a quick question, would you generate an age that is not static? As in, I need my date to be changing. My sample is from 2012-2016 and so the age has to change every year not for just December 31 2018 - Age variable. Thank you for your help it is much much appreciated.

[Enrico Zorzi]

Yours Age is for years 2012 -2016
the mean of Age for years

clear
input int Y2012 Y2013 Y2014 Y2015 Y2016
1 2 3 4 5
2 3 4 5 6
3 5 6 6 7
end
local Y "Y2012 Y2013 Y2014 Y2015 Y2016"
foreach x of local Y{
egen Mean`x'=mean(`x')
}

[David Benson]

You might try this (note that if they really were founded on 31-DEC-1997, you might want year_founded = 1998 instead of 1997.

dataex firm_id year date_founded_str  //  To install: ssc install dataex
clear
input byte firm_id int year str10 date_founded_str
1 2012 "31/12/1997"
1 2013 "31/12/1997"
1 2014 "31/12/1997"
1 2015 "31/12/1997"
1 2016 "31/12/1997"
2 2012 "31/12/2000"
2 2013 "31/12/2000"
2 2014 "31/12/2000"
2 2015 "31/12/2000"
2 2016 "31/12/2000"
3 2012 "31/12/2004"
3 2013 "31/12/2004"
3 2014 "31/12/2004"
3 2015 "31/12/2004"
3 2016 "31/12/2004"
4 2013 "31/12/2012"
4 2014 "31/12/2012"
4 2015 "31/12/2012"
4 2016 "31/12/2012"
end

------------------ copy up to and including the previous line ------------------

gen double date_founded = daily(date_founded_str, "DMY")
format date_founded %td
gen year_founded = year( date_founded)
gen firm_age = year - year_founded

. list, sepby(firm_id) abbrev(15) noobs

  +---------------------------------------------------------------------------+
  | firm_id   year   date_founded_~r   date_founded   year_founded   firm_age |
  |---------------------------------------------------------------------------|
  |       1   2012        31/12/1997      31dec1997           1997         15 |
  |       1   2013        31/12/1997      31dec1997           1997         16 |
  |       1   2014        31/12/1997      31dec1997           1997         17 |
  |       1   2015        31/12/1997      31dec1997           1997         18 |
  |       1   2016        31/12/1997      31dec1997           1997         19 |
  |---------------------------------------------------------------------------|
  |       2   2012        31/12/2000      31dec2000           2000         12 |
  |       2   2013        31/12/2000      31dec2000           2000         13 |
  |       2   2014        31/12/2000      31dec2000           2000         14 |
  |       2   2015        31/12/2000      31dec2000           2000         15 |
  |       2   2016        31/12/2000      31dec2000           2000         16 |
  |---------------------------------------------------------------------------|
  |       3   2012        31/12/2004      31dec2004           2004          8 |
  |       3   2013        31/12/2004      31dec2004           2004          9 |
  |       3   2014        31/12/2004      31dec2004           2004         10 |
  |       3   2015        31/12/2004      31dec2004           2004         11 |
  |       3   2016        31/12/2004      31dec2004           2004         12 |
  |---------------------------------------------------------------------------|
  |       4   2013        31/12/2012      31dec2012           2012          1 |
  |       4   2014        31/12/2012      31dec2012           2012          2 |
  |       4   2015        31/12/2012      31dec2012           2012          3 |
  |       4   2016        31/12/2012      31dec2012           2012          4 |
  +---------------------------------------------------------------------------+

[Iulia Andreica]

And how do you get the age in years, based on the year of incorporation of the firm?

[Nick Cox]

Age in 2021 = 2021 - year of incorporation.

[Iulia Andreica]

Thanks! but is there a command for this? Sorry, I am new to Stata.

[Rich Goldstein]

help generate

[Iulia Andreica]

Thank you!