I'm from Germany, here they tax gains in stock trade with a higher rate and the government tried to extend this higher rate on trade with stamps and other "art" formats multiple times, but realized its unfeasible and for now gave up. Currently you pay a whopping 25% in taxes on capital gains over ~1000$ and have other substantial losses. A few years back it could even climb as high as 50% if you were unlucky. Also you don't pay any special taxes here if you simply sell your private collection.
I think the current US tax rate on capital gains is at 0% if you earn little, 15% if your income is in a "medium" range and it can climb to 20% if your wallet is really thick.
This is not based on any personal research but on what my father told me, yet seeing how much time he is (and especially has been) spending in this field, that he keeps up to date, and that generally speaking he is a reasonably smart man, I have no reason to doubt his expertise in this topic. Naturally he's enthusiastic about this but he wouldn't warp facts. Every time I visit I unsually tend to leave with more insight in this field than I really want to. He also keeps close track on how the value of his private collection rose over the past, how it still rises, and I know what the figures look like.
Back on track, I should have made the disclaimer that I'm not really familiar with US tax law. The main point I'm making here however is that it is a very safe long term investment that is practically guaranteed to pay out substantially more than what you buy it for in the long haul. This should hold true regardless of what country you're from.
I wasn't aware you're not in the US. If your country has high capital gains taxes compared to income taxes, the balance might be different in the US. However, stamps and other collectibles have many problems:
-- Stamps can get stolen, lost, or burned in a fire. It's hard for this to happen to stocks (unless you're behind the times and have them as a pile of paper certificates)
-- If you buy a type of collectibles that you're actually interested in, your desire to keep a co llection of something you're interested in may lead to poor decision-making on a fi...
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.