Those 700,000 new homes

How was the figure derived? What MND says: The 700,000 housing units (public and private) are needed to meet demand from the projected population growth of 1.6 million persons and smaller household sizes in the future. Household sizes are expected to decline in the future due to our increasing single and elderly population. Non-residents such as Employment Pass holders living in Singapore also tend to have smaller households. Of the 700,000 needed, 200,000 homes are already in the pipeline, to be completed by 2016. To realise the remaining 500,000 more homes, we will need to develop new housing towns/estates, pockets of land in existing towns as well as redevelop/ intensify older housing areas.