-27cases is estimated to leap-frog to $20.8 billion... Another serious economic problem caused by an aging population is steep increases in healthcare expenditure.”67 71. The Government is undoubtedly right to regard the problems of our ageing population as serious and right to lay down policies aimed at mitigating those problems with a view to ensuring the long-term sustainability of our social welfare system. But what, if any, rational connection is there between such mitigation and the impugned policy of excluding new arrivals from receiving CSSA until they have resided here for seven years? I do not think any such connection exists. 72. Given that one of the root causes of the ageing population problem is Hong Kong’s low fertility rate, and given that the OWP scheme has become “the single most important immigration policy that shapes Hong Kong’s demographic growth and composition”, with Mainland new arrivals accounting for 93% of our population growth between 1997 and 2001,68 a rational response to the ageing problem ought to involve encouraging the entry of young immigrants to rejuvenate our population. This was recognized by the Task Force which acknowledged that: “...OWP holders, in particular young children, have contributed significantly towards mitigating the negative effects of low fertility and population aging by replenishing the dwindling number of our younger age cohorts.”69 73. As has already been pointed out, the Government has only partially acted on that logic, exempting those under 18 from the seven-year residence eligibility criterion for CSSA, but applying the restriction to parents who arrive to be reunited with and to care for such children. To that extent, far from the seven-year requirement being a rational measure to mitigate the ageing 67 At §§3.6 and 3.7. 68 Task Force Report §2.17. 69 Task Force Report §5.3.