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.