Ben McKay crystal-balls the caucuses and finds that on current polling, women are looking likely to lose out on both sides of the house.

Whether they win government or not in October, National is set for a big gain of MPs after the election. Does that mean their caucus will enjoy a big influx of women, of Māori, of LGBT representatives and fulfil Christopher Luxon’s goal of looking more like the society they hope to represent? Well, no.

Labour has a gender problem too. Their huge 2020 win delivered New Zealand a record number of women MPs – eventually a historic majority – as well as diversity in spades. Unfortunately, on current polling, it’s Labour women who will be leaving parliament as the Labour vote drops.

Candidate selection by the major parties is almost certainly going to produce a maler, and staler, parliament.

Let me start at the outset by saying this analysis will be wrong. There will be surprise electorate wins and losses, swings in the polls, and candidate shenanigans (like this all-timer) which mean the makeup of MPs won’t be known until New Zealanders vote for it. But with Labour completing its list rankings and National unveiling its candidates, if not a list, we can have an educated guess at where they’ll end up.

Fire up the predict-o-tron

Let’s set the scene. In the 2020 Ardernslide, Labour won 46 electorate seats to National’s 23. (That has changed since due to Meka Whaitiri’s defection and Gaurav Sharma doing a Gaurav Sharma, leaving Labour on 44 and National on 24.)

For the sake of this exercise, let's flip a bunch of electorates to be roughly in line with the current Spinoff polling average and just flat-out guess the Nats win 37 electorates to Labour's 30. Our assumptions here: Chlöe Swarbrick holds Auckland Central, David Seymour holds Epsom, Te Pāti Māori holds Waiariki, takes Te Tai Hauāuru and Meka Whaitiri brings Ikaroa-Rāwhiti over too. The rest are major party holds. Sorry Raf Manji, you've lost Ilam. And Brooke van Velden, you got close in Tāmaki but just missed out.

So Labour loses 13 seats to National. Let's assume they are the 13 most marginally held general electorates and flip the following:

Notice anything about those groups of candidates? Of the 13 likely National winners, they're retaining two male list MPs, bringing in eight new male MPs and just one new woman: Catherine Wedd in Tukituki. Noteworthy too is the makeup of the Labour losses: it's 11 women and two gay men. So Labour will also take a big diversity hit should this group exit parliament.

Let's now add the winners of the marginal seats to the existing National electorate MPs, who we'll presume all hold their seats given the swing to the Nats.

• East Coast Bays - Erica Stanford
• Kaipara ki Mahurangi - Chris Penk
• North Shore - Simon Watts
• Whangaparāoa - Mark Mitchell
• Botany - Christopher Luxon
• Pakuranga - Simeon Brown
• Tāmaki - Simon O'Connor
• Papakura - Judith Collins
• Port Waikato - Andrew Bayly
• Coromandel - Scott Simpson
• Hamilton West - Tama Potaka
• Taupō - Louise Upston
• Waikato - Tim van de Molen
• Bay of Plenty - Tom Rutherford
• Rotorua - Todd McClay
• Tauranga - Sam Uffindell
• Taranaki-King Country - Barbara Kuriger
• Rangitīkei - Ian McKelvie (retiring, replaced by Suze Redmayne)
• Kaikōura - Stuart Smith
• Selwyn - Nicola Grigg
• Waimakariri - Matt Doocey
• Waitaki - Jacqui Dean (retiring, replaced by Miles Anderson)
• Southland - Joseph Mooney
• Invercargill - Penny Simmonds

Of the 37 electorate MPs, there will be eight women, or 21%: Catherine Wedd, Erica Stanford, Judith Collins, Louise Upston, Barbara Kuriger, Suze Redmayne, Nicola Grigg, Penny Simmonds.

The next piece of the puzzle is determining how big National's entire caucus will be, and we'll keep running with those polling averages, plugged into the Electoral Commission's wonderful MMP calculator.

That means National is going to end up with 46 seats, and on our workings, will bring nine MPs off their list. Given they don't have a list yet, let's work that out for them. As a starting point, let's bring in the five MPs that are currently ranked in the party's top 20

1. Nicola Willis (2)
2. Paul Goldsmith (5)
3. Melissa Lee (13)
4. Gerry Brownlee (15)
5. Michael Woodhouse (17)

Another two women join the caucus: deputy leader Nicola Willis and Melissa Lee.

Now we get into very choppy waters. National is yet to do its list, but they have another three list-only candidates: Agnes Loheni, Nancy Lu and James Christmas. You'd imagine they weren't selected to be stocking-fillers at the bottom of the pile. Christmas and Loheni even get ministries in Audrey Young's fan fic National-Act cabinet piece. So let's give them all jobs, along with another sitting MP: Harete Hipango. Hipango forfeited the chance to stand in her old seat of Whanganui to instead run in the Māori electorate of Te Tai Hauāuru where National stands no chance. You'd imagine she would have only agreed if she would be rewarded with a high list ranking. Party sources deny this, but we're running with it for now.

1. Agnes Loheni
2. Nancy Lu
3. James Christmas
4. Harete Hipango

So that's it. The final result would be, in the 46-strong National caucus, 13 women, or 28%. Congratulations to Nicola Willis, Melissa Lee, Harete Hipango, Agnes Loheni, Nancy Lu, Catherine Wedd, Erica Stanford, Judith Collins, Louise Upston, Barbara Kuriger, Suze Redmayne, Nicola Grigg and Penny Simmonds. Commiserations to the sole current member of National's caucus who is standing again but doesn't back get in based on this speculation: Maureen Pugh.

It's not representative despite Luxon's desire – as reported by Claire Trevett in the NZ Herald – for a 50/50 gender split. In fact, on 28%, National may head backwards. The current caucus is 34-strong, with 11 women. That's 32%. The 54-strong caucus before the 2020 election had 19 women, or 35%.

There are other National women that have been preselected to winnable seats. Two are Napier's Kate Nimon and Dana Kirkpatrick in East Coast, both of whom aren't facing incumbents due to the resignation of Stuart Nash and Kiritapu Allan. If they get in, they'll dislodge two others from the list. In any case, Luxon is going to be well short of his 50-50 goal. But he is not the only major party leader with a women problem.

Let's now turn to Labour and run through its likely 40-strong caucus. We've given them 30 electorate seats: so let's assign the 26 general electorates with their biggest margins and their four Māori seat holds:

• Te Tai Tokerau - Kelvin Davis
• Tāmaki Makaurau - Peeni Henare
• Mount Albert - Helen White
• Mount Roskill - Michael Wood
• New Lynn - Deborah Russell
• Kelston - Carmel Sepuloni
• Te Atatū - Phil Twyford
• Panmure-Ōtāhuhu - Jenny Salesa
• Māngere - Lemauga Lydia Sosene
• Manurewa - Arena Williams
• Takanini - Neru Leavasa
• Hauraki-Waikato - Nanaia Mahuta
• East Coast - Tamati Coffey
• Napier - Mark Hutchinson
• Palmerston North - Tangi Utikere
• Whanganui - Steph Lewis
• Wairarapa - Kieran McAnulty
• Mana - Barbara Edmonds
• Remutaka - Chris Hipkins
• Rongotai - Fleur Fitzsimons
• Ōhāriu - Greg O'Connor
• Wellington Central - Ibrahim Omer
• Te Tai Tonga - Rino Tirikatene
• West Coast-Tasman - Damien O'Connor
• Wigram - Megan Woods
• Christchurch Central - Duncan Webb
• Christchurch East - Reuben Davidson
• Banks Peninsula - Tracey McLellan
• Dunedin - Rachel Brooking
• Taieri - Ingrid Leary

Labour will elect 10 off the list to get to their predicted 40 MPs – so let's give them away to the top 10 in their list that don't win electorates. We don't get very far. Returning to parliament are:

1. Grant Robertson (4)
2. Jan Tinetti (6)
3. Ayesha Verrall (7)
4. Willie Jackson (8)
5. Willow-Jean Prime (9)
6. Adrian Rurawhe (11)
7. Andrew Little (12)
8. David Parker (13)
9. Priyanca Radhakrishnan (15)
10. Ginny Andersen (17)

The top MPs to miss out: customs minister Jo Luxton at 19, rising star Camilla Belich at 26 and well-liked whip Shanan Halbert at 28. The new partyroom has just a handful of new faces: Reuben Davidson in Christchurch East, Fleur Fitzsimons in Rongotai and Mark Hutchinson in Napier, who is no sure thing given Stuart Nash's departure and the post-cyclone challenges.

Labour's gender split? Well they take a hit from their current 56% (35 of 62), and fall down to 47.5% (19 of 40). The impact is clearer when you consider who is losing out as Labour falls back to earth: the number of women in Labour's caucus falls by 16, whereas just six blokes lose their gigs.

We've come this far, so let's complete the exercise.

Under the poll average, Act is winning a bumper 17 MPs, that will include Brooke van Velden, Nicole McKee, Karen Chhour, Parmjeet Parmar, Laura Trask, Antonia Modkova and Toni Severin. Seven women, or 41% of its caucus.

The Greens are tipped to win 12 MPs, returning Auckland Central's Chlöe Swarbrick, and bringing Marama Davidson, Julie Anne Genter, Lan Pham, Golriz Ghahraman and Hūhana Lyndon in off the list. Six women, or 50%.

Te Pāti Māori will win five seats, and while they haven't unveiled their list, they feature just six candidates on their website, and all but Rawiri Waititi are women. Let's give them four women MPs, or 80%.

In all, the class of 2023 will have 49 women – 41% of the house, compared to just over 50% currently. The only party to have a smaller proportion of women than that, and substantially smaller, will be National. That is, unless Luxon grabs his party's as-yet announced list and shakes it up to meet his own gender goals.