The first expansion of parliament was passed in 1948, and came into force at the 1949 election. It was also the largest increase we’ve seen, either proportionally or in raw numbers. The House and Senate were each expanded by two thirds – the House grew from 74 to 121, while the Senate grew from 36 to 60.
This blog post follows the model of my previous analysis of the 1984 parliamentary expansion, and will likewise be the first of two parts.
The collection of data is much messier for 1949 than for 1984. For a start, the collection of full preference counts only commenced in 1983 (backdated after legislation was passed after the election). And the calculation of two-party-preferred estimates in every seat usually date back to 1949, not 1946.
The 1946 election (and to a lesser extent 1949) also were less purely two-party than politics in the early 1980s. There were four non-classic races in 1949, and six in 1946. I have been able to estimate two-party-preferred figures for all seats in 1946 and 1949. For the 1946 results adjusted to the 1949 boundaries, I have used estimates produced by Colin Hughes in a 1978 paper.
First up, how does the 1946 results compare to the notional seat count following the redistribution but prior to the election?
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Labor’s share of seats was about steady. I have matched Coalition seats to the primary party at the 1949 election. The new seats benefited the Liberal Party much more than the Country Party, before factoring in Coalition gains at the election.
This next chart shows the proportion of seats that have a particular Coalition 2PP (or less) before and after the redistribution.
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While a stable 2PP produces the same result on old and new boundaries, Labor does better if the 2PP is slightly lower or slightly higher. The old boundaries gave less than half of the seats to Labor with a 2PP of 53% or more. The new boundaries gives Labor 52% of seats on that 2PP.
The next question to consider was where the marginal seats were located before and after the redistribution.
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The proportion of seats with margins under 6% slightly dropped overall, but it varied more in each state. New South Wales and Queensland gained more marginal seats, Victoria had less, and South Australia and Western Australia a lot less.
As with the 1984 redistribution, I’ve produced a map showing the old and new boundaries. Seats with 2PP margins of under 6%. The NT and ACT aren’t included in this analysis, as their members weren’t full voting MPs at this time. Unfortunately my historical boundaries dataset is missing Western Australia’s 1949-54 boundaries, so the map only shows WA’s pre-redistribution map.
The 1948 expansion was much larger than the 1984 expansion – 64%, rather than 18%, and the map understandably changes quite a lot more. A lot more rural seats were marginal than today, and not many urban seats, but it does look like the expansion shifted the marginal seats slightly into the cities.