Proper installation with a seatbelt involves engaging the retractor so it has basically no play at all.
It's true that improper installation is quite common, though.
> The LATCH system is seems to be bolted on, but not always used. It’s still going to bounce in a crash as the seat cushion has a lot of give under these forces.
A forward-facing seat using LATCH should usually be installed with three point LATCH (the third is over the seat back), so without much play in any direction, certainly not forward.
Two point LATCH can move up-down and side-to-side a bit, but still not forward.
"While it may be possible that an improperly installed car seat may not be any more effective than a seat belt alone, and that probably accounts for at least some of the Freakanomics data, that is a SOLVABLE problem. Ditching the car seat is one “solution,” but I would argue that a much better solution would be to meet with a child passenger safety technician to make sure your car seat is being used in a manner that would keep your child as safe as possible. “Other people don’t use car seats correctly, so I won’t use one at all” is a rather absurd conclusion, don’t you think?"
That point aside, the bigger one is that they concentrate on fatalities more than injuries, where there is a ton of data on the effectiveness of seats for children older than 2.
Generally speaking, Freakonomics does raise many interesting points that make you think more critically about causality. But more often than not they end up drawing a blanket conclusion that is as lazy and un-nuanced as the one they claim to have debunked.
That's not going to explain the data. The numbers require seat belts to be about as safe as car seats for children 2+ on average. Thus, unless an improperly installed car seat was significantly worse than an average seat belt, it's all kind of a wash.
Anyway, this is more about public policy than individual choice. If your spending public money to promote something it must increase the average safety levels or your wasting peoples money.
PS: As to improper use, when swapping multiple car seats it’s very easy to forget to attach one. With seat belts it’s more visually obvious their not in use. That’s a huge safety risk and could account for the unexpected data.
Otherwise it’s difficult for something to meaningfully reduce injuries without also preventing deaths. Unless you have a better explanation?
latch/isofix has limitations which is why it's not the de facto install mechanism across the board. there's a 65lb weight limit on most anchors (including the car seat - which can be 30+lbs by itself), and most sedans don't have a set in the middle rear seating position but a lot of people will incorrectly install it that way.
it is okay for a car seat to have a little give. they're designed not to be installed so tight it damages your car in the process. rear facing car seats will sometimes flip into the seat back and 'cocoon' in more severe accidents, and that's by design.
The LATCH system is seems to be bolted on, but not always used. It’s still going to bounce in a crash as the seat cushion has a lot of give under these forces. Further, in terms of real world companions you need to understand people don’t nessisarily use safety equipment correctly especially if it’s more time consuming. Comparing LATCh attachment vs seat belts is a whole other discussion.