I have data which look something like this.
company  date  auditor  change  count
A        2016  ZXY      0       1
A        2015  ZXY      0       2
A        2014  ZXY      0       3
A        2013  FPQ      1       4
A        2012  ZXY      1       5
B        2017  ERW      0       1
B        2016  ERW      0       2
B        2015  ERW      0       3
B        2014  ERW      0       4
B        2013  ERW      0       5
.
.
.
.
This data tells whether auditor has switched in last five year. If there is switch then change value is '1'. I want to calculate
1) Percentage of companies who had switch in last year (count=1).
2) Percentage of companies who had no switch in last five year (change=0 for count=1,2,3,4,5).
3) Percentage of companies who experienced change more than once in five year (change=1 for count= more than once)
I just want the logic of how to do it.