The researchers looked at how monetary and fiscal policies affect housing markets in Portugal and Spain from 1996 to 2019. They found that changes in monetary policy don't impact housing prices, but fiscal policy does. Specifically, fiscal policy shocks have a significant effect on housing prices in both countries. The differences in housing markets between Portugal and Spain can be linked to their varying fiscal policy approaches, while the common monetary policy set by the ECB doesn't seem to make a difference.