Tax relief for access to homeownership also accounted of a significant share of homeownership support in a number of countries, especially where it was designed as non-means-tested mortgage tax relief - a regressive and distorting measure. This measure alone costed 0.36% of GDP on average in OECD countries, 0.5% of GDP in the United States and a staggering 2.3% of GDP in the Netherlands - well above the amount spent by the country on targeted housing allowances and social housing put together. As a consequence, the reported numbers are a lower-bound estimate and errors are likely to be larger in countries who do not report spending on tax relief for mortgages (see note to Figure 9). In 2009, the government estimated about 400 000 dwellings were sub-standard either because of poor construction material, lack of basic facilities or high overcrowding (OECD, 2012).