Are you the sort of investor who embraces the buy-and-hold strategy, preferring to do your due diligence up front and then let the returns accumulate over time? If so, index-based exchange-traded funds (ETFs) may be a good vehicle for you. Even Warren Buffett knows it's hard to beat index funds. In fact, he made a point of requesting that 90% of the money he leaves his wife when he dies be invested in an S&P 500 index fund. (See also: Proof That Buy-and-Hold Investing Works.)

Of course, you don't have to park all your money in an S&P 500 fund. In fact, most experts recommend some diversification. But as far as long-term investments go, indexed funds are an attractive and typically low-cost choice. (See also: Here's How to Build Wealth Like a Multimillionaire.)

If you're doing some portfolio planning for 2017 and beyond, here are a few good bets for ETFs that work for long-term investors. All year-to-date (YTD) performance figures are based on the time period of Jan. 1, 2017, through August 3, 2017. Funds were selected based on a combination of performance and assets under management (AUM). All figures were current as of August 4, 2017.

Vanguard Total Stock Market ETF (VTI)

  • Issuer: Vanguard
  • Assets Under Management: $81.96 billion
  • YTD Performance: 11.07%
  • Expense Ratio: 0.04%

If you're not sure which index to follow, or you want to hedge your bets across a variety of sectors and market caps, this is the fund for you. As the name implies, the Total Stock Market ETF covers the entire domestic stock market, tracking the CRSP U.S. Total Stock Market Index. VTI is a balanced fund, with a good mix of mid- and small-cap equities in addition to blue chips. The median market cap is about $54 billion. You'll also see good sector diversification among the 3,528 stocks in its basket.

VTI is an extremely efficient fund with a low expense ratio, which is perhaps why the fund has raked in nearly $10 billion in new assets since the end of 2016. Performance figures are steady and impressive, with one-year, three-year and five-year average annual returns of 17.29%, 10.61% and 15.08%, respectively. (See also: Is VTI The Best Index Fund?)

SPDR S&P 500 ETF (SPY)

  • Issuer: State Street Global Advisors
  • Assets Under Management: $241.82 billion
  • YTD Performance: 11.72%
  • Expense Ratio: 0.09%

This is the granddaddy of ETFs – the oldest and most easily recognized of the exchange-traded funds. It tops the list in terms of AUM and trading volume, making it appropriate for both tactical traders and buy-and-hold investors. The fund tracks the S&P 500, which is a group of equities from the U.S. large-cap space (although not always the largest) selected by committee.

Technically, SPY is a unit investment trust (UIT), which means that the fund can't reinvest cash dividends between distributions, a minor detail that may slightly affect performance compared with the index. Regardless, this fund has respectable one-year, three-year and five-year performance figures at 17.13%, 10.97% and 14.99%, respectively. (See also: Top 3 ETFs to Track the S&P 500 for 2017.)

Vanguard Dividend Appreciation ETF (VIG)

  • Issuer: Vanguard
  • Assets Under Management: $24.86 billion
  • YTD Performance: 10.79%
  • Expense Ratio: 0.08%

Long-term investors should not overlook the portfolio boost of dividends, and VIG is a great choice for this space. This ETF tracks the Nasdaq Dividend Achievers Index, which carefully screens out companies with heavy debt or other perceived measures of financial weakness. The fund invests only in companies that have shown dividend increases over each of the previous 10 years.

There are currently 188 stocks in the VIG – large-cap companies representing a blend of value and growth. Equities are heavily tilted toward industrials and consumer goods, with household names like Microsoft Corporation (MSFT) and Johnson & Johnson (JNJ) in the top 10 holdings. Three-year and five-year performance figures (9.85% and 12.76%) are very respectable for a dividend fund. (See also: A Look Inside the Vanguard Dividend Appreciation ETF.)

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