-1.87% is the change from 321 to 315
Calculation steps:
[( 315 - 321 ) ÷ 321] x 100 = -1.87%
Formula
Percentage change = [(315 - 321) / 321] x 100
Subtract the new number by the original number
315 - 321 = -6
-6 ÷ 321 = -0.018691588785046728
-0.018691588785046728 x 100 = -1.87%