It has long been known by investment analysts that optimising risk and return (which is their job) is achieved by tracking the market. Experienced managers, analysts and data all consistently say that, if you want to invest in the stock market buy the index. And hold it.
Young bucks, and old, would like to beat the market. Some might do so for a limited time period. But no one has consistently done so. Why? Because to beat the market you have to consistently do better than everyone else. That is cocky and statistically very unlikely.
The opportunity to make better bets than everyone else has declined in recent years as computerised portfolio management and trading has grown and index investing has become the principal approach of behemoths which control sizeable fraction of global share trading, like BlackRock.
In addition, some data suggests that taking higher risks can in fact lower your expected return, as appeared to happen in the 2000s. We are now 9 years into a bull market with little regulatory reform, growing political uncertainty and upward pressure on interest rates (which might attract capital from equities to debt).
The people who beat the market are the ones who take fees (from you) for handling money, or have inside information.
There are reasons to choose a narrower portfolio of listed equities. You might want to restrict your investment to a country, region or industry, or avoid places or sectors. But to try to pick stocks requires a consistent focus and adaptability. If you are going to do it yourself, fine. But if you are paying someone else, they generally have an incentive to take risks with your money that they mightn’t with their own. And of course their fees eat in to your capital.
So, simply, if you wish to diversify your savings beyond property (your home usually) or debt (bank deposits etc) by putting some in the stock market be careful not to be blinded by the attraction of “expected return” ignoring the danger of risk, and the cost of fees. So buy a low load (i.e. low fees), index (i.e. market tracking) fund.
And remember, most people make money by working, not gambling. Gambling is more likely to break your fortune than make it.
The following article by The Economist (11 June 2016) offers further insight.
Asset management: Index we trust
Vanguard has radically changed money management by being boring and cheap