How much the typical American has invested outside of retirement accounts at every age

Growing wealth with investing doesn't happen overnight, and nothing shows that more clearly than comparing balances of Americans at different ages. 

Wealth management company Personal Capital gathered data on over 328,500 investment accounts linked to its platform for users ages 20 to 70. The data looked at non-retirement investment accounts, including things like brokerage accounts, non-qualified annuities, and both individual and joint investment accounts. The data does not include IRAs or 401(k) accounts, excludes spouse accounts, and excludes outliers of over $100 million. 

While the typical 20-something has a median account balance of just over $10,700, the typical 60-something has over $210,000. Between ages 20 and 40, values of investment accounts at least double between each age bracket. The smallest increase is between age 50 and 60 — around the time when people start to become more conservative with their investments as they approach retirement.

Investing strategies are most effective in the long-term

Building wealth through investing doesn't happen overnight, and the balances of each age group indicate that clearly. Starting to invest early helps immensely, even if you feel like you don't have much to show for it in the beginning. 

In investment accounts, compound interest — the process by which interest earns interest on itself, growing an investment account's balance quicker than it would otherwise — means that starting early helps to grow money quicker.

An example by Business Insider's Tanza Loudenback illustrates this starkly. In this calculation, two people started saving for retirement (note that retirement accounts are investment accounts) with the same 5% return rate and $100 monthly contributions. However, they started 10 years apart. The person who started 10 years sooner has $73,000 more at age 65, but only contributed $12,000 more over the years.

Long-term investing is an expert-recommended strategy for people who want to grow their wealth through investing. A long-term buy and hold method, where you hang onto your investments for decades as the market weathers ups and downs, is a favorite of famed investor Warren Buffett. Some investors swear by dollar-cost averaging, where they invest a given amount of money in the market at regular intervals (monthly, for instance), regardless of how the market is looking.

The commonality in these two strategies, and in any long-term investing strategy, is that the investors aren't trying to time the market — put money in when they think the market will rise and take money out when they think the market will fall. Experts say that time in the market is much more important for building wealth, because timing the market accurately is borderline impossible for the average investor.

Like any other type of wealth-building, investing takes time.