"Equity investing" => Bad English?

[patran]

Hi, I was told by my English teacher that there is no such thing as "equity investing", only "investing in equity" or "equity investment". However, I found that in Economist, "equity investing" is used in their article. I am afraid to bring the article to ask my teacher as she doesn't like people challenging her. May I have some other teachers here to tell me if "equity investing" which I think is referring to the action, is good English?

Below is the abstract I found from Economist (I can't put the link here coz I dont have enough posts here)

Equity investing
Buy, hold, regret
Sep 13th 2011, 8:43 by Buttonwood

IT IS a truth universally acknowledged that equities outperform over the long term, so that the best strategy is to buy and hold. But as Deutsche Bank's long-term asset study makes clear, this has not been true for all markets. Over the last 50 years, the real returns from equities have been lower than those from bonds in Germany, Japan and Italy. In the Italian case, the gap is almost three percentage points, and that is despite the recent bond sell-off (actually, as Deutsche points out, a 5-6% yield on Italian debt is quite low by historical standards.)

[SoothingDave]

If you check the dictionary, it gives "equity" as a noun and not an adjective. That said, I don't think most people would object to its use as an adjective in the phrase "equity investments."

English evolves.

I remember a footnote in a materials science textbook I had in college. It pointed out that Oxford had a school not for "Materials Science" (as other colleges did), but "The Science of Materials." Because Oxford is famous for its dictionary and they insisted that "materials" is not an adjective

Materials science - Wikipedia, the free encyclopedia