I will admit that I was a bit off-the-cuff in terms of the Western aspect of my comment.
There are lots of factors, of course, and the trend isn't limited to only the west. Though it has certainly become a more normal trend in developed and developing countries than those with a higher level of poverty and poor.
I still contend however that it has never been easy. My grandparents had four children starting at age 20. My grandfather's first job was sweeping floors in a factory at age 13, making $0.30 an hour. When he asked for a raise, he was fired. He said he didn't have two nickels to rub between his fingers.
His father before him went into World War 1 at 15 years old. And his father (my great-great grandfather) falsely signed the documents affirming that he was 18 years old, to allow his own 15 year old son to go to war.
They struggled, but didn't complain. Some part of it is cultural expectation, and that has changed greatly over time. In spite of all odds my grandparents raised four fairly middle class children in these circumstances, but had a good few decades of strife. Whether or not they would create a family and procreate was taken for granted. It was assumed, at their own economic expense. But long-term family wise, today my grandfather has a tree of descendants who love him.
I think today we are more conscious of the economic equation. We ask whether or not we can afford to provide for children, rather than letting them exist and then asking how we can provide for them. There is an aspect of this that I appreciate, but I worry that it's mixed with some amount of narcissism. Though I am an atheist, there is some unreason to our existence in the first place, and there is hope in the continuance of ourselves that we should value beyond economics. There is a romance and some type of spiritual value in being able to put aside the cost-benefit analysis and simply bear new life that is part you, to have and to hold, to love, teach, and reciprocally learn from.
We have so much bounty today that the idea of "sacrificing" ourselves for something that only has potential value is an alien concept. As our material wealth has increased, and as our understanding of personal economy has evolved, I think we've lost a bit of our primal, but beautiful, nature that wants ourselves to persist at a biological, cosmic level.
You, here, right now reading this are the absolute last leaf, the most extended branch, the most outstretched and sun-bleached arm of a tree of life that has been proceeding for four billion years. You are the last link in a chain that has not been broken for four billion years. Can you believe that? Every time I consider that, I think of my parents. And I ask, who am I to be so conceited that all of that history, that fourth of a fraction of the universe, should end with me?
I'm not sure where I'm going with this, and, I will confess that I got a little tipsy for the super bowl. Don't judge me too harshly. But life is beautiful, and beauty is always difficult to sustain. We do it because beauty contains a truth and a promise for the future. And I think that's something we need to put effort into re-evaluating, and re-valuing, in our current world.
One line of inquiry might be why there is a correlation between bounty and the general wealth of an economy, and the fertility rate. Many parts of the world that are poorer are more fertile, and reproduce more unquestionably. Korea is rich and the rate is 0.84. In the Congo the rate is 6.21. It is not about economics. And if you counter that it is about poor education or care, I don't believe that's the reason either. It's culture, and values.
Paul Revere had 15 children. 5 of them died young, and he still had 10. He had a horse and a rifle and a small wooden house you can still tour in Boston. Today we have DINKs, and people who are in what is considered to be the low-income range with multiple rooms in big cities, an education, and combustion-engine vehicles who say it's too expensive to have children. Maybe your tastes are too expensive. Maybe you've been raised softly, and don't know how to set yourself aside to rear and participate in a family that is spiritually worth more than just yourself.
One of the other comments said I ranted so I thought I'd actually provide one. Sorry HN, I hope I made some sense here.