Image: Vanguard Group.

Most people know they need to save for retirement, but many are intimidated by the complexity of the investing world. To make investing for retirement simpler, many financial companies have created target date mutual funds that combine a number of different investments into a single package. The Vanguard Target Retirement Fund series is one such fund, created by the Vanguard Group as a way for people to get everything they need to save for retirement in a single investment. Let's look at the Vanguard Target Retirement Fund and why it could be the simplest way to long-term riches for you.

The basics of Vanguard's Target Retirement Fund
The first thing to know about the Vanguard Target Retirement Fund is that you actually have 12 different mutual funds from which to choose. Funds corresponding to target dates every five years ranging from 2010 to 2060 make up the bulk of the offerings, and a single fund aimed at providing income for those already in retirement closes out the list.

The idea behind the Vanguard Target Retirement Fund is that investors should pick the fund that corresponds to the year they expect to retire. Over time, the fund goes from a more aggressive mix of assets when you're young and still have a long time before retirement to a more conservative asset allocation as you grow older and approach the end of your working life. For instance, the 2060 fund is composed of 90% stocks and 10% bonds, while the 2020 fund has a much larger 40% bond allocation and just 60% in stocks.

Vanguard isn't the only company offering target date funds, but the advantage of using Vanguard is that you gain access to the low-cost funds the index fund pioneer is famous for promoting -- with index funds connected to the stock and bond markets both within the U.S. and internationally. The funds tend to favor domestic investments but still have significant foreign exposure, giving investors diversification. Another benefit of using Vanguard's index funds as underlying investments is that the expense ratios on the Vanguard Target Retirement Fund are very low, ranging from $16 to $18 per year for every $10,000 you have invested.

The downsides of the Vanguard Target Retirement Fund
All that said, Vanguard's target date funds are far from perfect. One criticism is that you can duplicate the funds' portfolios yourself by buying the underlying index funds directly and save some expenses. With those component funds charging between $5 and $19 annually per $10,000 investment -- and most of the allocated money going to the cheaper part of that range -- wealthy investors can save hundreds or even thousands of dollars each year just by monitoring their balance on their own.

Also, not all investors agree that index funds are the best strategy for long-term investing. Some competing target date funds offer actively managed mutual funds rather than index funds; while they're more expensive, top funds can sometimes earn a sufficient extra return to offset higher costs.

Finally, like any other target date fund, the Vanguard Target Retirement Fund takes the decision about asset allocation out of your hands and puts it squarely on Vanguard's shoulders. That's fine when things work out, but during the financial crisis many target date funds took heat for being too heavily invested in stocks. If you're not comfortable with the level of risk that Vanguard's target date funds take, then you'll probably prefer to create a do-it-yourself mix of funds on your own.

The Vanguard Target Retirement Fund series isn't the only way to invest for retirement, but it is one of the simplest. With basic exposure to the most important investments you'll need and extremely low costs, a Vanguard Target Retirement Fund can be a great way to build up your retirement savings over time.