Malthus and macroeconomics provide only a partial picture of the deeper motives for the trend.
I believe the biggest motive is Yuppie self-absorption promoted by rampant materialism, unchecked by spirituality. Why bother to have babies when the prospect exists for almost indefinite life extension? Hence the spiraling market for nutritional supplements, personal care products and services, and rejuvenation treatments.
Watch for renewed worries about a First World population explosion of oldsters after medical investigations of immortality-promoting drugs begin to bear fruit within the next fifty years.
Whole new sets of questions about the absolute and relative values of life, innovation, economics and wealth distribution caused by these "advancements" will make today's arguments look like sandbox warfare.
"a First World population explosion of oldsters"
I'm waiting for the "revolt of the workers", who refuse to pay in to a "social security" program in which each of them is supporting 1.5 retirees.
In my Christian homeschool group, children are regarded as blessings. Many families have 5 or more. Often when I speak to more secular parents, they often think we are crazy because we enjoy having our kids all day.
Their attitude is kids are a burden and and drain on their pocketbooks, and that they tie them down.
Thanks for your insightful, (and alarming), post. Unfortunately, there are still many people guffawing at spiritual admonitions like yours, believing that government and/or science will save us all from the unprecedented crisis of declining populations caused by "a woman's right to choose". It's paradoxical that legalized abortion is not only decimating populations and throwing the future of nations into doubt, but it's also helped create the narcissistic mentality that blinds people to this fact.
IMHO, moden taxation/welfare state....historically one motivating factor for children was to have someone to care for you with aging. Modern taxation interferes with having resources for family, and a welfare state implies no need for worrying about who will care for you with age.