Akuko Nkwupụta Azụmaahịa Harvard: A na-eji ihe dị ka nde awa 4 kwa ụbọchị na UK na nzukọ otu, na United States, nkezi 1,100 nzukọ otu kwa ụbọchị, nke ọ bụla n'ime ha bụ awa 3.5 kwa ụbọchị, ọ bụghị otu awa.