-31.87% is the change from 251 to 171
Calculation steps:
[( 171 - 251 ) ÷ 251] x 100 = -31.87%
Formula
Percentage change = [(171 - 251) / 251] x 100
Subtract the new number by the original number
171 - 251 = -80
-80 ÷ 251 = -0.3187250996015936
-0.3187250996015936 x 100 = -31.87%