The electoral map in Australia looks a little different this election compared to the 2013 poll.

Western Australia has gained a seat, New South Wales has lost one and a swag of seats across both states and the Australian Capital Territory have different boundaries.

The changes are a result of redistributions — a process the Australian Electoral Commission (AEC) uses to ensure that each electorate has a relatively even number of voters.

It also ensures that each state has a representative number of seats in the House of Representatives.

So how does the AEC determine the boundaries? And how does it assess the impact of a redistribution?

One curious Australian has asked us to investigate.

When does redistribution happen?

The AEC has three triggers to conduct redistributions:

When the number of MPs which a state or territory is entitled to changes. This figure is calculated by the Electoral Commissioner a year after every election, taking into account the latest population statistics

When the number of MPs which a state or territory is entitled to changes. This figure is calculated by the Electoral Commissioner a year after every election, taking into account the latest population statistics When the number of voters in a third of seats in a particular state or territory deviates significantly from the average (over 10 per cent for a period of more than two months). But ABC Election Analyst Antony Green said this rarely, if ever, happens

When the number of voters in a third of seats in a particular state or territory deviates significantly from the average (over 10 per cent for a period of more than two months). But ABC Election Analyst Antony Green said this rarely, if ever, happens And the so-called "seven year rule", when seven years or more has lapsed since the last redistribution

While NSW, the ACT and WA have undergone recent redistributions, other states are due for a shake-up in the near future.

The Northern Territory is currently mid-redistribution, Tasmania is overdue, Queensland's due later this year, Victoria next year and South Australia in 2018.

How do they do it?

The first step is to form a Redistribution Committee.

This is usually composed of the Electoral Commissioner, the Australian Electoral Officer for the state/territory under review, and two state/territory government appointees - the Surveyor General and the Auditor General.

The Redistribution Committee applies a quota for each seat based on the state's population three-and-a-half years ahead.

For instance, the quota in the recent NSW redistribution was calculated by taking the state's projected population in 2019 (5.195 million) and dividing it by 47 seats. That left a projected quota of 110,542 voters for each NSW seat.

The committee draws up a proposed redistribution that considers the current boundaries, geography, communication and travel within a proposed electorate; and economic, social and regional interests.

The public (or nervous politicians) have four opportunities during the process to have their say by commenting, suggesting or objecting to new boundary proposals.

Once they are finalise by the Commission, the Parliament has no power to reject or amend the new boundaries.

Mr Green points out the recent redistributions in NSW and WA made the Coalition's task of retaining government harder.

"The redistributions reduce the Coalition from 90 to a notional 88 seats, while Labor increases from 55 to a notional 57 seats," he said.

These notional figures are calculated using new estimated seat margins, calculated by both the AEC and the Parliamentary Library using polling data from the previous election.

What's in a name?

The NSW Labor seat of Throsby was re-named Whitlam after the former Prime Minister. ( Australian Information Service/National Library of Australia: nla.pic-an24355082 )

Here is a curiosity — electorates can only be named (or re-named) in a redistribution.

In the most recent redistributions, the NSW Labor seat of Throsby was re-named Whitlam in honour of one former prime minister.

In the ACT, the seat of Fraser, originally named after former local MP Jim Fraser, was renamed Fenner, in honour of scientist Frank Fenner.

It seems the Fraser name is being saved for a future Victorian seat to honour of another former leader, Malcolm Fraser.