Rising crime rates make people withdraw their faith in social engineering because they are one of the most vivid and immediate experiences that prove how limited the social engineers are in their knowledge, power, and benevolence. Falling crime rates make people think, "Gee, whatever the social engineers are doing seems to be working," renewing their faith in planning and authority, even if they are not responsible for the decline.
One group that has kept at its missionary activity throughout these rising and falling crime periods, however, are the Mormons. In their Wikipedia article, I found the following chart, which shows how many converts were baptized into the Church, compared to the number of missionaries. This gives a rough measure of productivity or effectiveness -- for every missionary out there proselytizing, how many converts could he expect to win over? I can't immediately find data going back before the 1970s to give a longer-term picture.
Yep, that same pattern emerges again -- moving one way during the '70s and '80s, and turning around after that. Missionaries are sent to a great diversity of countries, and it's unlikely that their local trends for crime rates or cocooning are going to synch up with our own. So this rise and fall probably reflects a rise and fall within American culture -- something affecting the missionaries themselves, rather than how ripe the foreign cultures are for conversion.
From the same article, on the recent low levels of conversion:
Author David Stewart points out that the number of convert baptisms per missionary per year has fallen from a high of 8.03 in 1989 to just 4.67 in 2005. He argues that the number of converts would increase if Mormon missionaries made greater efforts in meeting new people; he points out that the average pair of missionaries spends only four or five hours per week attempting to meet new people.
If he's proposing a change in order to reverse a decline, he must have good reason to believe that the missionaries used to spend more time meeting new people during the '80s than they do in the 21st century. That would fit with the peak being in '89, after which time Americans began cocooning (according to various domains of life that I've posted on over the last several years).
Leading up to that, Americans were growing more outgoing and socially savvy, so missionaries were growing more and more adept at the people skills needed to convert others. But now that young people spend so little time interacting with each other -- or anyone else, for that matter -- while they're growing up, they aren't going to feel comfortable heading off to a foreign land to proselytize. They're too socially awkward.
This case provides clear evidence for what I've been saying about the stunting effects of helicopter parenting, and their near irreversibility when the parents finally decide it's OK for their little darlings to (try to) leave the nest. You have to give your kids experience interacting with genetic strangers, building a sense of autonomy, and honing a knack for social negotiation, when they're little and keep it going. That way, when they're 18 or however old, they're capable of getting by without social intervention from mommy and daddy.
In the mind of helicopter parents, they're only delaying the major milestones of development -- not preventing them altogether. Their kid will grow up normal, just at a slower pace than the parents themselves grew up. But there is a sensitive window of time for all things developmental, the obvious example being language. Don't talk to your kid until he's 12, and he won't master language ever.
Here, we see that just throwing a bunch of socially sheltered boys into a strange new place where they're forced to interact with strangers won't make up for their entire infancy, childhood, and adolescence being spent locked away from non-nuclear family outsiders (including peers). The missionaries have 2 full years to convert others, so if they could quickly make up for lost time, they shouldn't turn out too differently from the missionaries of the '80s, whose childhoods were a lot more inclusive of folks outside the nuclear family.
But the fact that they're less than 60% as successful as their '80s counterparts suggests that those two entire years away from the family are too little, too late.
You see the same thing when Millennials head off for college, at the same age as the missionaries. For their whole lives, they've been prevented from socializing with peers unsupervised, so how do you expect them to turn out when they're no longer under direct parental supervision? That they'll suddenly know how to give and take appropriately, that they'll have an instinct for where boundaries are, or that they'll know how to respond and adapt across a range of situations? They've only been told how to act by their supervisors, not discover it for themselves and develop an intuition.
It's no surprise that they remain locked in their own little world, preferring the familiar security of their cyber-cocoon, and tensing up with dread at the thought of really getting to know new people, in a more than superficial way.
What is the fate of young people with no intuition for where the boundaries are, and no intuition for what the norms are, once the parents are no longer there to provide direct instruction? Parents might worry that they'd go hog-wild and embarrass themselves. And certainly a tiny handful of college kids do that every year. But in general, a sense of bewilderment about social boundaries and norms leads a person to fear leaving the private sphere in the first place. It would be like sailing an ocean for the first time without a map, compass, or ability to interpret weather conditions.
If that means their kid will remain landlocked for life, well maybe that's the point all along. Helicopter parents have never trusted the outside world, so it's the lesser of two evils that their kid become stunted and dependent on the parents, rather than gain autonomy and venture off into the corrupting outside world.