What is a percent change describing a deacrease in a quantity?

Percent Increase

It changes when the market demand and or market supply changes.

Percent change is the percent amount some value has changed. It has phenomenal usage in every day math and in fields such as business. It's often used to calculate the percent difference in sales...

Divide the new number by the original number, subtract '1', and multiply by 100.

percent of increase- new-original over original then make the decimal a percent of increase percent of decrease- original-new over original then make the decimal a percent of decrease