-19.3% is the change from 171 to 138
Calculation steps:
[( 138 - 171 ) ÷ 171] x 100 = -19.3%
Formula
Percentage change = [(138 - 171) / 171] x 100
Subtract the new number by the original number
138 - 171 = -33
-33 ÷ 171 = -0.19298245614035087
-0.19298245614035087 x 100 = -19.3%