A decrease in solidarity means people have fewer resources to turn to in time of crisis.
With a decrease in solidarity, a man either makes it on his own or fails on his own.
If a man is struggling to make it on his own, a child becomes an unwelcome hindrance. A child is an economic drain, and if a man has no other resources, a child might destroy his chances of success.
Thus it should come as no surprise that programs to provide economic aid to poor soon-to-be-parents would decrease abortion rates to some extent.
However, without solidarity, there is a backlash to this. As long as economic aid comes via governmental handouts, the broken solidarity continues to wither for want of attention.
Thus it should come as no surprise that programs to provide economic aid to poor soon-to-be-parents have either a temporary influence on abortion rates, or are incapable of decreasing abortion rates beyond a certain point.
A lack of solidarity has also led to dramatic divorce rates of around 50% as a whole. As bonds between us are cut, the true reasons to marry become obscured.
As the true reasons to marry become obscured, more people seek sexual congress outside of marriage. This has several effects, among which are single-parenthood and poverty. Fear of single motherhood and fear of poverty both are leading causes of abortion.
Socialism is a mechanism that destroys solidarity by placing the government between people. Capitalism is a mechanism that destroys solidarity by placing markets and the maximizing of profit between people. As a note, by capitalism I mean the materialistic philosophy in which increasing capital is the primary goal.
Seeking to attack abortion via socioeconomic programs targets the superficial reasons why a pregnancy is unwelcome. It does not work to change the underlying mentality–sex without consequence–and in fact, these programs work more to subsidize that mentality.
Seeking to attack abortion via legislation seeks to reintroduce risk into sex, thus attacking the free-sex mentality. Unfortunately, this does not address the entitlement mentality that feeds, maybe even begets, the free-sex mentality.
Now, does a loss of solidarity lead directly to the entitlement mentality? I can see that loss of solidarity leads to government spending which leads to the notion of entitlement, but that has an intermediate step. Or is it the case that loss of solidarity and the entitlement mentality are brethren, rather than one being the cause of the other?