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!