If you're looking for a "percentage change" from Condition A to Condition B, always use Condition A (the starting point) as the denominator in the calculation.
“The lower number” is condition A, so what’s your point?Don't be confused by the posters who tell you to "divide by the lower number."
That's the right answer in this case, but not in every case.It would always be right provided that the change was an increase. Alberta's Child’s formulation also works when the change is a decrease.But “subtract the smaller number from the larger” yields a similar, but not correct result in that case. The result will be similar but not correct, and will also of the wrong sign - positive, when it should be negative.