Correlation of number of (non mining) full nodes to internet bandwidth Are there any correlation studies showing the number of (non mining) full nodes per country (total or per/capita) compared to average internet connection speeds?

I know there are great differences between connection speeds depending on ISP and if the users are in rural or urban areas.

The time to download an entire blockchain from scratch for maximum security can take a very long time in some places. I want to know how much this discourages people from using full nodes (in favor or SPV wallets).

Comparing average connection speed to number of full nodes (per capita) in each country is what I am looking for.
I don't think any such study exists, because it is very difficult to gain any concrete information about full nodes on the network.  Because nodes can (and often are) run over proxies or TOR, their true IP addresses are often obscured.  Furthermore, IP addresses aren't necessarily a good indicator of geographic location, and certainly not connection speed.

Even if you identify a node in a country with generally poor residential bandwidth, the operator of that node could be running it from a commercial data center that has much better connection speeds than the average for that country.  Attempting to sort full nodes into residential and commercial categories would be almost impossible.

It sounds like you're trying to do something similar to this:  Bitcoin node Decentralization