The change in the number and distribution of registered voters, due to population shifts and housing developments, determines how electoral boundaries are drawn, the Electoral Boundaries Review Committee said in its report, received by the Prime Minister on Tuesday.
It "reviewed all the existing electoral divisions, taking into account their current configurations, population shifts and housing developments since the last boundary delineation exercise", the report said.
There are an estimated 2,460,977 electors as of Aug 1 this year, which is 110,720 more than in 2011.
This means each of the 87 elected Members of Parliament today has an average of 28,300 electors.
The committee worked on the basis of a range of 20,000 to 37,000 voters per MP, allowing for a variation of 30 per cent as in past practice. In comparison, the range in 2011 was between 20,000 and 36,000 voters per MP. The only anomaly - which the committee did not explain - is single-seat Potong Pasir, which has 17,389 electors and whose boundaries remain unchanged. The seat was opposition-held for 27 years, until 2011.
The committee, which was formed in May, was also tasked to reduce the average size of Group Representation Constituencies (GRCs) to below five, and to have at least 12 Single- Member Constituencies (SMCs).
With the changes, which have been accepted by the Government, the total number of elected MPs will rise to 89 from the current 87.
This comprises 13 from SMCs and 76 from GRCs, up from 12 and 75 respectively in 2011.
The committee was also mindful that a GRC with fewer MPs should not have more voters than a GRC with more MPs. It proposed that the number of four-MP GRCs go up to six, from two, and that there be eight five-MP GRCs, down from 11. The number of six-MP GRCs remains at two. The average number of MPs per GRC will thus be 4.75, down from five in 2011.
The five-member committee is chaired by Mr Tan Kee Yong, secretary to the Prime Minister. Its other members are Housing Board chief executive Cheong Koon Hean, Singapore Land Authority chief executive officer Tan Boon Khai, Department of Statistics chief statistician Wong Wee Kim, and Elections Department head Lee Seng Lup.