using singaporean babies cohort size as a guesstimation, the 70s/80s cohort is 36,000 there abouts , they marry within the same age group, and 30% remain single, (36000 x 0.7)/2, at least 12,000 should be built a year...
from 2001-2005, 55,000 flats were built, which corresponds to the 70s/80s cohort size
from 2006-2010, 26,319 flats were built, which is grossly inadequate to supply born and bred Singaporeans
HDB is under building for the years 2006-2010, for born and bred singaporeans