shrink·age 
/ˈʃrɪŋkɪʤ/ noun
/ˈʃrɪŋkɪʤ/ noun [noncount] 1 : the amount by which something becomes smaller or less
▪ The shrinkage in contributions is significant. ▪ a shrinkage of 10 percent 2 : the act or process of becoming smaller in amount, size, or value
▪ the shrinkage of the polar ice caps
▪ The shrinkage in contributions is significant. ▪ a shrinkage of 10 percent
▪ the shrinkage of the polar ice caps
