One way is to ascribe it to the residual after all other factors have been controlled for (“excess growth”) (see Annex A 1.6, White, 2007). Given that technological change occurs over time, a time index is another logical way to control for the effects of technological change on health expenditures (see Annex A1.10, (Di Matteo, 2005). Tw'O models (A1.3 and 1.24) among those reviewed used a direct measure of specific technologies. On average across the OECD, demographic effects are projected to have a small impact on expenditure growth of 0.7 percentage points from 2005 to 2050.