That's not the issue. This issue is that if property taxes are relatively low in Spain, as I think they might be, both relative to the US (where property taxes are among the highest due to the rather extreme form of federalization and multiple local governments practiced there) and to other European countries, then implementing a property tax increase is likely to be a very effective way of reducing Spain's deficit and making the wealthier pay for it, instead of service cuts or public sector wage cuts. But if property taxes are already high, as they are in many parts of the US, there won't be a lot of extra tax revenue to be gained that way.