The Australian Stable Population Party has identified the root of all our problems. It's too many people. Housing too expensive, too many people. Traffic jams, too many people. Overcrowded schools, too many people. And they have a solution, no more people. From the current population of 23 million, they want us to aim for 26 million at 2050. By my rough calculation, this would require us to stop all immigration and reduce the birth rate to about 75% of it's current level1.
They have a few ideas on how to achieve this. First is zero net immigration, where immigrants are only allowed in when someone emigrates. This means effectively no immigration2. They'll also end the unrestricted immigration of New Zealanders, so any Kiwis who want to come over Second is a getting rid of financial support for children beyond the second, so no birth payments or parental leave for the third kid and beyond. Doing it this way seems a bit harsh, although to be honest I'd rather see the birth payment gotten rid of entirely, but then again quite like the this idea from Finland.
They also feel that what's good for the goose is good for the gander and wants to tie foreign aid with recipients making efforts to reduce their population growth.
Given Australia's rather low population density, I disagree with their rather low numbers for what can be sustained. People have been predicting Malthusian catastrophe's since Malthus in 1798 and it's not happened yet. I think better infrastructure using better technology, more support for high density housing, better mass transit, and so forth would allow us to support many more people in our cities.
They have avoided taking a stand on other policy matters, thinking that population is the be all, end all of concerns. They are running candidates for the senate in every state and territory, plus a handful of house of representative candidates.
1) given a current population of 23 million and a target of 26 million for 2050, assuming a constant rate of growth for the population, the rate of growth r = (26/23)^(1/35) = 1.0035 (I used 35 years instead of 37 as it's a rounder number). For this year that would mean a population gain of 80,000. In 2011 (the most recent year I could find ABS stats for) there were 297,903 births and 146,932 deaths, net growth 150,971 or twice the desired level. Reducing the births to 75% of what it was gets a net population growth of around 75,000, about the level suggested.
2) Emigration of citizens is pretty much balanced out by returning citizens, not leaving much for immigrants under a zero net immigration policy. ABS Migration stats