Both the Coalition and Labor have a preponderance of women in marginal seats, which impairs MPs’ ability to focus on advancement

If the Coalition is to tackle the gender gap that is obvious in its federal ranks, then there are strong arguments that Wentworth needs a woman as its local member.

Last week Andrew Bragg, a former Liberal party director and frontrunner for the blue-ribbon seat, bowed out, saying it should go to a woman. A meeting to decide on preselection for Wentworth is set for Thursday evening and voters head to the polls on 20 October. Bragg’s decision was probably made easier by the fact he is likely to get a winnable Senate seat at the 2018 or 2019 election.

But his point about putting women into safe seats was well made.

It is not just about the number of women preselected, though this is important. During the 2016 election, both major parties congratulated themselves on preselecting the highest number of women ever: Labor 59 (40% of all candidates) and 44 (30% of candidates) for the Coalition.

But as the Guardian’s number crunching below shows, a disproportionate number of these women candidates were in unwinnable seats or marginal seats.

The attrition due to being put in unwinnable seats is clear: there are currently 13 women in the House of Representatives for the Coalition and 29 in Labor’s ranks.

With the two women independents, the total number of women in the House is 44 seats held by women in the 150-seat chamber.

But when one looks at the breakdown of women in safe or even fairly safe seats, the barriers to women flourishing in politics – in either party – become a little clearer.

Both major parties have a preponderance of women in marginal seats. This means their lives in Canberra are going to be spent with one eye on their future survival and how they are being perceived back in their electorates. Energy must be spent on the local, not the big picture.

Safe seats, on the other hand generally mean job security, longevity and an ability to focus on political advancement within the party rather than survival in the electorate.

For example, Julie Bishop is in the safe seat of Curtin in Western Australia, which she holds with a 21% margin. Without diminishing her talents, this job security has given her latitude to play a major role in the Liberal party in WA, raise funds and campaign for colleagues (important for internal advancement in the party room) and travel the world as foreign affairs minister. Would her success have been possible if she needed to attend local school events and sports club barbecues each weekend?

It is also worth noting that, with the exception of the former prime minister John Howard, whose seat of Bennelong became increasingly marginal due to redistributions, Australia’s postwar prime ministers and opposition leaders almost always come from safe or fairly safe seats. And if they don’t, they have been known to relocate, as Kim Beazley did.

In the case of the Coalition, there are just six women in safe seats with margins greater than 10%. This is only 17% of the Coalition’s safe seats.

In Labor, it is a little better but the prizes of safe seats still fall mainly to men. There are 10 women in safe seats, which is 34% of those seats with a margin of 10% or more.

Labor also does better than the Coalition on selecting women into winnable places in the Senate – a chamber which allows more focus on policy and political backroom dealing than electorate matters.

The ALP has put in place affirmative action policies in the party rules, which aim to ensure that 50% of elected representatives are female. The Coalition has no such formal policy. The statistics show Labor’s policy is working, but slowly.

Unless both parties focus on the need to put women into safe seats in the same proportion as men and free them from the responsibilities of holding onto marginal seats, both are destined to see under-representation on their frontbenches and as leaders for many years to come.