Whom to cite from an article: the reporter or the person who provided a quote to the reporter?
To add to Allure's suggestion, I think it would be most appropriate to make a slightly longer citation like


  According to (Corak, reported in Younglai 2016)


You stated that you didn't want to include both names, but I think it is more helpful to the reader that way. Additionally, the above citation tries to be not too wordy (compared to yours), as it is just a footnote inside the parentheses rather than disrupting the flow of text.

The ideal, of course, would be that you find a paper originally published by Corak or some other academic that identifies this phenomenon (the "theory/concept" you mention), but you may not have the time to do a detailed dig through the literature.