Generating count variable for observations per year

[Joe Cullen]

I have the following (simplified) dataset

Person_ID	Fiscal_Year
101	2015
101	2015
101	2016
102	2016
102	2017
102	2017
103	2015
103	2016
103	2017

I would like to generate a variable that counts the Person_ID's per Fiscal year.
So, for example, the variable should contain the value 2 because the person ID is two times in the Fiscal_Year 2015.

The values of the new variable should be as follows:

Person_ID	Fiscal_Year	New_Variable
101	2015	2
101	2015	2
101	2016	1
102	2016	1
102	2017	2
102	2017	2
103	2015	1
103	2016	1
103,	2017	1

Could anyone help me out?

Thnx in advance!

[Carlo Lazzaro]

Joe:

. bysort Person_ID Fiscal_Year: egen counter=count( Person_ID )

. list

     +-------------------------------+
     | Person~D   Fiscal~r   counter |
     |-------------------------------|
  1. |      101       2015         2 |
  2. |      101       2015         2 |
  3. |      101       2016         1 |
  4. |      102       2016         1 |
  5. |      102       2017         2 |
     |-------------------------------|
  6. |      102       2017         2 |
  7. |      103       2015         1 |
  8. |      103       2016         1 |
  9. |      103       2017         1 |
     +-------------------------------+

.

[Nick Cox]

Or just

 
 bysort Person_ID Fiscal_Year: gen counter = _N

[Joe Cullen]

Thnx a lot both of you!