How do you determine whether a CSS property requires browser specific prefixes?

I recently looked at the following question:

How to disable text selection highlighting开发者_C百科 using CSS?

Which nicely provided the answer to the immediate CSS problem I was facing. However, it made me wonder, how do you determine when it is safe to drop all the browser specific prefixes for CSS properties?

I know how the mechanics of this work, older browsers which require a prefix will of course always need a prefix, so I suppose the answer really depends on the browser usage statistics.

Is there a decent, simple, source of reference that can be used to determine whether all these prefixes are really required for a CSS property, e.g. if I use the user-select property without prefixes, I can guarantee 95% of browsers will interprit this correctly.

This is an excellent summary of browser support for pretty much every CSS property.

However, I tend to use the browser-specific prefixes, as well as the non-specific rule, no matter what - it's not exactly much extra work and it will mean those few people stuck on outdated browsers still see the page as you intended.

One good resource I've used for this sort of thing is http://caniuse.com/. In general, it is not a bad idea to have a list like, for example,

-webkit-border-radius: 3px;
-moz-border-radius: 3px;
border-radius: 3px;

For the space of a few lines, this ensures that older browsers will get the right browser-specific rules if they require them, and that newer browsers get the standards-compliant rule.

Edit: Well, I noticed that the resource to which I linked does not have an entry on user-select. Oops!

I've found this to be the best resource for that:

http://www.w3schools.com/cssref/css3_browsersupport.asp