The study examined research from member countries of the Organization for Economic Cooperation and Development. The economists found, for example, that eight out of ten Haitians and Jamaicans with college educations live outside their countries.

In southern Africa, skilled workers are just four percent of the workforce. Yet they are forty percent of the migrants from the area.

是否可以理解为：在南非，技术工人仅占总劳动力的4%，其中技术移民就占了技术工人40%的比例。

from the are 怎样理解？

你的翻译是错误的。
应该是：在南部非洲（包含南非以及其他国家，只说南非是不准确的！），技术工人仅占总劳动力人口的4%，而移自这些地区的技术工人却占这一地区外出移民总数的40%！
from that area 是指来自南部非洲。
翻译要结合上下文，上段的意思是：据世界经合组织的研究：十分之八的海地和牙买加受过大学教育的人都移居国外。