Professor David Albert Jones:

We have more evidence for the countries where it is longer established. We have evidence of what happens, and I think those are the places you should look for evidence. I also think the tendency in all countries that have had it for a reasonable amount of time is toward expansion; an expansion of category as well as expansion of numbers. You should therefore look to those places like Canada and Belgium, which are more expansive, to see where this might go. You should not just think about where this legislation or this practice might start, but where it might realistically go. I think therefore you should look at the more expansive countries, and not think that the ones which have recently had more restrictive laws will maintain those laws.