Some forecasts predict a decline in the total population within the next 100 years. Birth rates in many countries (not just industrial, first world) have dropped below replacement rates for long enough that we'll likely see a plateau in total population, and possibly a drop, as there won't be enough young people having babies to replace the big bubble of old people that all start to die off together.
There's a fixed amount of resources. So you can only manufacture, grow and produce to a limited extent - even if all the production is automated. You can use the greater quantity of resources per person to provide more affluent lifestyles to everyone.
Think of it this way: if there is enough energy to support 80% of the people in a typical USA suburban lifestyle, but you have instead 60% of the people. The excess can be used to give the people more per capita. Providing "more" in whatever sense requires greater productive output.
That's the first thing, resources.
The second is occupation of time. Not all people need to be employed all the time but with an excess of resources one can concentrate on attaining a higher level of education, healthcare, etc.. These things in turn require more focus on training, more intelligent input to push on to give a greater quality of life for everyone.
Yes, more people create greater needs. But with resource limitation and wealth being focussed with a small group those needs simply don't get met, there is not so much more employment as is needed to meet those needs with a degree of quality. Instead what happens is resources get stretched - austerity measures and such.
There's also the corollary of economies of scale. Greater production requires a decreasing number of additional personnel. Going the other way this means there is a point at which even if you produce less you still need a similar number of people to do it.
[Would be happy to get feedback on holes and flaws in this thinking though.]
Your resources argument is sound, for a certain time frame, i.e. long enough that we are worried about running out of resources on earth, but short enough that we haven't developed the technology to extract resources off of earth.
However, unemployment is not currently (and isn't likely to be in the near future) caused by limited by natural resources, so I don't see how freeing up more resources will help with unemployment on any reasonable time scale.
Furthermore, more resources don't solve the problem of unemployment. More resources per person may allow us to provide a better quality of life for the remaining people, but it won't create jobs.
In fact while you may have some arguments for a better quality of life with fewer people (assuming resource limitations and ubiquitous automation, and assuming that 10 people living at X standard of living is inherently better than 100 people living at less than X standard of living), none of the arguments directly address solving unemployment. I was specifically challenging the previous poster on that point. Will population reduction solve unemployment. It may solve other "problems", not unemployment.
I'm not suggesting mass genocide. If family planning is right for a family then surely it's right for a nation and for nations together?
If we keep increasing the population at this rate it seems that it won't end well.