Although this "study" was based on back of the envelope estimates, and the 1/3 estimate is probably inaccurate, there is anecdotal evidence of large-pursed foreign investors from around the world -- not just China but Australia, Russia, etc -- who are sustaining, if not increasing the demand for housing in populous areas.
This foreign investment is great for people who are trying to sell a home in one of these markets but horrible for buyers, who can't compete with all-cash fast-close-best-price offers. Further, the few realtors who are boots-on-the-ground for these investors have market insights -- they know what's potentially about to go on the market but hasn't yet, get insider information, etc -- and use this information asymmetry to their advantage by offering on homes even before any real home buyers have a chance or offer on the first day of listing! I have personally gone through losing multiple times to these sorts of customers while trying to buy a new home (in the NYC metropolitan area on the NJ side), not an investment property.
The experience of buying a home in a high-demand housing market where institutional/major investors are participating really challenges my thinking about whether free market practices should be allowed to operate in housing at all. Considering the rising cost of housing, it is tough to side with capitalism on this subject.
I'd like to see a study about the "artificial growth" of housing prices by investors. Interestingly to note is that such a study may conflict with the agenda of at least some leading universities who tend to publish reports about rising cost of housing after receiving generous funding from housing investors. NYU Furman, for instance, has a long-lasting public relationship with Capital One (and god knows who else in private).