How high does the Fed need to push mortgage rates to kill purchases?

?This is a market as resistant to higher interest rates as you could possibly imagine,? said Christopher Thornberg, founding partner at Beacon Economics in Los Angeles. ?This is not a market that 5% interest rates are going to scare at all.?

https://www.wsj.com/articles/the-fed-searches-for-the-magic-number-to-cool-a-red-hot-u-s-housing-market-11653402996?mod=hp_lead_pos5

I have no idea what Christopher Thornberg is talking about.  Applications for purchase mortgages are tanking like crazy, and new home sales numbers are even more abysmal.