<prompt> Human: Last year, my bank in an EU country set the interest rate of savings accounts to 0, and there are even banks with a negative interest. Ive been wanting to look into investing for a while now, but this was the last straw to finally go and do it.So looking around, Ive read about different kinds of investments, one of which are ETFs. And somehow, to me, they look kind of magical well, some of them. And I dont understand why.So for example, looking at an ETF which tracks the SP 500 index, I can see that in the past its value has risen by 17 over the past year, roughly 18 in 2016, and about 77 over the last 5 years which if Im correct corresponds to about 12 per year on average. And this just seems ridiculously high. If I understood everything correctly, if I had bought 10k of ETFs 5 years ago, they would now be worth about 17.7k.This is just one example. There are a few others as well which seem really stable. Of course, there are also those which fluctuate a lot.And from my research, Ive typically seen that lower risk investments will gravitate more towards 5-10 growth per year. Investing in the stock market yourself could net much higher, but its a lot more work and a lot riskier. A lot of companies stock fluctuate wildly all the time, so its not a case of set it and forget it.So, after all my research, I feel like Im missing something. That there is some sort of a catch to these stable, growing ETFs that Im overlooking. And I want to be completely sure of that before I dump a few thousand euros on these, thinking that theyre low risk.The only thing I can see from past performance, taking this SP 500 index tracking ETF as an example again, is that it tanked hard in 2008 no surprise and it took over 5 years to recover to the same value. But keeping tabs on it, it should be quite possible to tell when such a trend sets in and sell, and then wait until the upwards trend comes again or, play it safe and invest elsewhere with lower risk at that point. Of course, historical data is no guarantee for the future, but since the entire economy tanked at that time, this particular ETF was not the only victim.  <response>: But keeping tabs on it, it should be quite possible to tell when such a trend sets in and sell, and then wait until the upwards trend comes again or, play it safe and invest elsewhere with lower risk at that point.This is where youre wrong. This is easy to state but impossible to predict what will happen to stocks in the future 