"Percentage decline" refers to the amount by which something has decreased in relation to its previous value, expressed as a percentage. It shows the extent of the decrease compared to the original value. Full definition
This is an incredibly large number and that is why even the relatively small percentage decline in prices last year has put the entire economy at risk. (mybudget360.com)
For the second year in a row, the highest percentage declines came under this category. (cde.ca.gov)
I used absolute declines, though the results look similar if percentage declines are used instead. (canadianbusiness.com)