Truth is that historical data performance is not an indicator of future performance. That said, the answer to your question depends on a number of factors, such as what are you seeking to invest in. Is it actively managed funds, hand-picked stocks or index funds? Do you expect a long-term return of your investment or are you after short-term, high-risk gains etc.?
For example, if you think that a market crash is imminent, it does not make sense to invest in equity only (and as a popular opinion, it does not make sense to do that generally, as your portfolio needs to be diversified to reduce the risk).
If you are thinking about a mixture of equity and bonds or bonds only, that's a safer bet in case the market crashes. This doesn't mean that you won't lose any money this way in the short term, but it means that there is reduced chance for your investment to take longer to recover. My answer is vague because I cannot talk based on facts, only what is a good general practice.
What makes most investors lose money in a market crash is panic. People that do not expect this are afraid the market is not going to recover ever again and thus prefer to withdraw their investment and make a moderate loss, than keep investing with the hope that it will recover, as experts suggest. So far, it has always recovered.
This monevator article is a good read that might provide a better answer than I have.