Average year over year change in FTP?

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Taking the last two to five training years into account, what has been your average year over year change in FTP (note per year):

Drop of greater than -5%?
Drop from -5 to -2%?
Little change -2 to +2%?
Increase from +2 to +6%?
Increase from +6 to +10%?
Increase from +10 to +15%?
Increase greater than 15%?