Calculating the amount of Board Turnover - stata

Question

I have been trying to calculate the amount of turnover happening in exective boards between 2006 and 2009 in the financial sector.
For this I have data looking like the following:
Year Bank Director DirectorID (ISIN, RoA, Size etc)
2005 Bank1 John Smith 120
2005 Bank1 Barry Pooter 160
2005 Bank1 Jack Sparrow 2070
2006 Bank1 John Smith 120
2006 Bank1 Barry Pooter 160
2006 Bank1 Jack Sparrow 2070
2007 Bank1 John Smith 120
2007 Bank1 Barry Pooter 160
2007 Bank1 Jack Sparrow 2070
2008 Bank1 John Smith 120
2008 Bank1 Carla Jansen 250
2008 Bank1 Jack Sparrow 2070
2009 Bank1 John Smith 160
2009 Bank1 Carla Jansen 250
2009 Bank1 Mike Stata 875
And this data repeats for each bank from 2005 - 2015.
Now I have already made a turnover dummy variable with 0 = no change and 1 = change by using:
collapse(sum) DirectorID, by (ISIN, Year, Bank)
gen interest = inrange(Year, 2006,2009)
bysort ID interest (DirectorID) : gen temp = DirectorID[1] != DirectorID[_N]
replace temp = . if interest==0
bysort ID : egen changed = max(temp)
However, I would like to make turnover an actual variable on how many changes were made i.e.: (assume bank2 made no change Turnover=0, bank3 made 6 changes (6 new managers came in)Turnover=6 and bank4 made 4 changes (4 new managers came in)Turnover=4.
Bank Turnover (ISIN, RoA, Size, etc)
Bank1 2
Bank2 0
Bank3 6
Bank4 4
Is this possible with Stata (or SPSS if that happens to be the case)?
ISIN codes are my ID variable as they are linked to each specific bank.
Two new people entered the board of Bank1. For now it would show as Turnover = 2 as only 2 new people entered the organization's board. Had three people joined in the previous example, in that case Turnover = 3 as each change made to the Board counts as "+1" turnover regardless of the people leaving. Only people that join (whether they replace someone or are just an addition to the board) are of interest in my thesis.
However, this could also be calculated differently if that makes it easier. Depends on how I write my methodology. It would be fine if the variable turnover says how many changes were made per year i.e. Turnover2005: 2005 - 2006, Turnover2006: 2006 - 2007, Turnover2007 2007- 2008 and Turnover2008 2008 - 2009
Finally, it's possible that TMTs grow, i.e. 2005 bank 1 has 14 managers on the board and in 2006 they hire 3 new managers but only let 1 go. Now the board has 16 managers and made 3 changes (3 new managers)

Answer 1

This might help. The following code builds a dataset consisting of data with four banks and five years. It is panel data. The xtset command lets you use time series operators which are well documented here (https://www.youtube.com/watch?v=ik8r4WvrPkc). (Note: for sake of clear exposition, in this example Bank 1 had no changes, Bank 2 had two changes, Bank 3 had three, etc.).
// Clear the session and other memory.
set more off
clear all
// Input reproducible data.
input year bank_num ceo_num
2005 1 200
2006 1 200
2007 1 200
2008 1 200
2009 1 200
2005 2 222
2006 2 222
2007 2 222
2008 2 333
2009 2 444
2005 3 300
2006 3 301
2007 3 302
2008 3 302
2009 3 303
2005 4 999
2006 4 888
2007 4 777
2008 4 666
2009 4 555
end
// Declare the panel structure.
xtset bank_num year
// Gen variable indicating if ceo_num stayed same.
// Resulting variable is 0 when there was no change.
gen no_turn = (ceo_num - f1.ceo_num)
// Gen dummy to indicate if ceo_num changed.
gen is_turn = (no_turn != 0 & no_turn < .)
// Gen a variable that counts changes.
egen turn_nums = sum(is_turn), by(bank_num)
// List data to inspect results.
list
Edit: Re-characterized comment for no_turn variable.