They sort of weaken their own premise, first saying that:
"In the past two decades house prices have doubled in real terms"
Then saying:
"Most empirical work shows that a 1% rise in the housing stock leads to a 2% fall in prices and rents, all else being equal. On that basis, a mass-downsizing would imply a cut in prices of about 5%."
When things have doubled in price, getting 5% off isn't really much help, especially when, as they noted, purchase taxes have gone up considerably.
"In the past two decades house prices have doubled in real terms"
Then saying: "Most empirical work shows that a 1% rise in the housing stock leads to a 2% fall in prices and rents, all else being equal. On that basis, a mass-downsizing would imply a cut in prices of about 5%."
When things have doubled in price, getting 5% off isn't really much help, especially when, as they noted, purchase taxes have gone up considerably.