From the WSJ:
But borrowers are undeterred. During the first eight months of the year, 75%, or 5,656, of private jumbo ARMs that were originated for home purchases had a fixed rate period of just one year...Homeowners are also refinancing with 1/1 ARMs. In August, 96% of the private-investor jumbo ARMs were for a 1/1, up from 84% in January, according to LPS.The article does not say what % of jumbo loans were for ARMs vs fixed rate. But 1/1 ARMs are a flip/speculation vehicle, not for long-term homeowners.