Hi Marie,
Measure the change by taking the new value and subtracting the old value
2000  1500 = 500
To express this as a proportion of the old value, divide by the old value
500/1500 = 1/3 = 0.333
Finally to express this proportion as a percentage, multiply by 100
0.333 100 = 33.3
Thus the percentage change from 1500 to 2000 is 33.3%. Since this is positive you might call this a percentage increase. If the change had been from 1500 to 1200 then the change is
1200  1500 = 300
so the percentage change is
^{300}/_{1500} 100 =  20, that is 20%.
Another way to say this is that a going from 1500 to 1200 is a 20% decrease.
Penny
