A proposal for discussion

[cif5000]

Over a decent period (e.g. 10 years) increase the Special Account contribution rate by a significant amount. This will reduce the amount available for housing payments.

I think this has already been done although it might not be significant enough. Look at the contribution rates for "35 and below" and you will find that the SA has increased from nothing to 5.5% over a span of 11 years. The amount available in OA is also reduced through the lowering of CPF Ceiling.

CPF Contribution
Total (Employer/Employee) into OA, SA and MA
Jan 1999: 30% (10%/20%) into 24%OA; 0%SA; 6%MA
Apr 2000: 32% (12%/20%) into 24%OA; 2%SA; 6%MA
Jan 2001: 36% (16%/20%) into 26%OA; 4%SA; 6%MA
Oct 2003: 33% (13%/20%) into 22%OA; 5%SA; 6%MA
Jul 2007: 34.5% (14.5%/20%) into 23%OA; 5%SA; 6.5%MA
Mar 2011: 35.5% (15.5%/20%) into 23%OA; 5.5%SA; 7%MA
Source: http://mycpf.cpf.gov.sg/Members/Gen-Info...ntriRa.htm

CPF Ceiling
Apr 2000: $6,000 to $5,500
Jan 2005: $5,500 to $5,000
Jan 2006: $5,000 to $4,500