aged 15 to 34, compared with 28 per cent of our population. Only 2 per cent of permanent immigrants are 65 or older, compared with 13 per cent of our population." Because of these statistics, Gittens claims that immigration is slowing the ageing of the Australian population and that the "net benefit to the economy is a lot more clear-cut." Robert Birrell, director of the Centre for Population and Urban Research at Monash University, has argued: "It is true that a net migration intake averaging around 180,000 per year will mean that the proportion of persons aged 65 plus to the total population will be a few percentage points lower in 2050 than it would be with a low migration intake. But this ‘gain’ would be bought at the expense of having to accommodate a much larger population. These people too, will age, thus requiring an even larger migration intake in subsequent years to look after them." In July 2005 the Productivity Commission launched a commissioned study entitled Economic Impacts of Migration and Population Growth, and released an initial position paper on 17 January 2006 which states that the increase of income per capita provided by higher migration (50 percent more than the base model) by the 2024–2025 financial year would be $335 (0.6%), an amount described as "very small." The paper also found that Australians would on average work 1.3 percent longer hours, about twice the proportional increase in income. Using regression analysis, Addison and Worswick found in a 2002 study that "there is no evidence that immigration has negatively impacted on the wages of young or low-skilled natives." Furthermore, Addison's study found that immigration did not increase unemployment among native workers. Rather, immigration decreased unemployment. However, in 2005 the Productivity Commission concluded that higher immigration levels would result in lower wage growth for existing Australian residents. On the impact of immigration on unemployment levels, the Commission said: "The conclusion that immigration has not caused unemployment at an aggregate level does not imply that it cannot lead to higher unemployment for specific groups. Immigration could worsen the labour market outcomes of people who work in sectors of the economy that have high concentrations of immigrant workers." Gittins claims there is considerable opposition to immigration in Australia by "battlers" because of the belief that immigrants will steal jobs. Gittins claims though that "it's true that immigrants add to the supply