Gilmore is the Illawarra's fastest growing electorate, with more than 5000 extra residents enrolling to vote this year.
According to the Australian Electoral Commission, there are now 101,464 in the region's southernmost seat, which is bounded by Warilla and Barrack Heights to the north and includes centres such as Kiama, Nowra and Milton-Ulladulla.
The Cunningham voting pool grew by 3.3 per cent to 104,109 and Throsby grew by just 2.6 per cent to 98,402.
Cunningham, which includes the University of Wollongong, is the Illawarra's youngest electorate, with a boost of 775 extra voters aged 20 to 24.
Throsby experienced a decline of 169 voters in this age group, and a drop in voters under 40.
All three electorates experienced a decrease in the number of 18 and 19-year-old voters, as well as voters between 35-39 and 45-49.