However you define them, cryptocurrencies have become hard to ignore since Bitcoin’s meteoric rise to $20,000 last December (as of May 2, it’s now $9,145 after a recent selloff). While past performance is of course no guarantee of future results, we’ve analyzed the last 16 months of action in digital tokens to shed light on what to expect if—as crypto diehards say—you decide to HODL (hold) despite the FUD (fear, uncertainty and doubt).

Are they financial assets, currencies, commodities or something entirely new? Bitcoin and other cryptocurrencies have defied easy categorization since they burst into the public consciousness last year, fueling an intense debate over how they should fit into the average investor’s portfolio—and whether they belong at all.

The crypto fever has quieted down, but the roller-coaster trading has raised the stakes for investors to figure it out.

This won’t come as a surprise to anyone following Bitcoin’s wild swings, but volatility and virtual currencies go hand in hand. That can be a good thing when values are rising (It hit $10,000! Now $20,000!). But it’s scary when markets are going south, one reason why investors tend to demand higher returns from more volatile asset classes.

Over the past 16 months, cryptocurrencies have recorded bigger swings than stocks, bonds, commodities and traditional currencies. The few non-crypto investments that are as rocky as most tokens included shares of Steinhoff International Holdings NV, the South African company embroiled in an accounting scandal, and bonds issued by Bank Otkritie FC, the recipient of Russia’s biggest-ever financial bailout.

Extreme volatility is perhaps the biggest argument against treating cryptocurrencies as you would the dollar or the euro. One of the cardinal rules for a good currency is that it should provide users with a stable store of value. You wouldn’t want to spend Bitcoin on groceries today if you thought the cryptocurrency’s value might soar tomorrow, or take your salary in Bitcoin if you thought it might plunge.

Bitcoin Towers Above Its Peers

Compared to stocks or bonds, trading activity and market capitalization among cryptocurrencies are very concentrated within a small group of players. While Bitcoin has become less of an outlier in recent months amid the rise of so-called alt-coins like EOS and Litecoin, the original still towers above its peers.

Among the most traded stocks, market values are relatively evenly distributed

In contrast, Bitcoin dominates the crypto market, both in terms of trading volume and market value. Liquidity dwindles sharply for smaller coins

One takeaway for investors is that selling lesser-known cryptocurrencies may be more difficult than it appears. Buying these smaller tokens should be thought of as like early-stage venture capital investing, which often involves holding an investment for a long time, according to David Drake, founder of multi-family office LDJ Capital, which invests in cryptocurrencies.