When bond yields are low, investors turn to dividend stocks to get the income they need. You can buy individual stocks if you want, but many investors prefer to use exchange-traded funds that offer them instant diversification across a number of key sectors of the dividend stock universe.

There are dozens of ETFs that specialize in dividend stocks. But for 2018, it's important to try to drill down on areas that many dividend investors never consider. Below, you'll learn more about Vanguard International Dividend Appreciation (NYSEMKT: VIGI), WisdomTree U.S. SmallCap Dividend (NYSEMKT:DES), and ProShares S&P 500 Aristocrats (NYSEMKT:NOBL) and why they're worth a closer look for investors.

Dividend ETF

Assets Under Management

Expense Ratio

1-Year Return

Vanguard International Dividend Appreciation

$825 million

0.25%

28%

WisdomTree U.S. Small Cap Dividend

$2.11 billion

0.38%

11%

ProShares S&P 500 Aristocrats

$3.63 billion

0.35%

24%

Data source: Fund providers, ETFdb.com.

A different type of Vanguard fund

Vanguard has a number of strong dividend ETFs, but this one doesn't get a lot of attention. Drawing on the success of its domestic counterpart, Vanguard International Dividend Appreciation focuses on stocks across the globe that have a track record of consistently growing their dividend payouts over time. The yield on the fund isn't all that impressive, having made distributions over the past 12 months amounting to about 1.8% of the ETF's share price right now. Yet the investment objective for the fund acknowledges that fact, making current yield less important than future payments.

Vanguard invests around the world, with almost 45% of its assets invested in Europe and another quarter in emerging markets. Pacific stock exposure amounts to almost 20%, with North America outside the U.S. picking up most of the remainder. With almost 250 stocks in the portfolio, Vanguard International Dividend Appreciation gives you the diversification you want, and its expense ratio is relatively low for specialized international ETFs.

Blue-colored graphic with word Dividends and small boxes with various sector symbols.

Image source: Getty Images.

Thinking small

Small-cap stocks aren't well-known for their lucrative dividends, largely because up-and-coming fast-growing small companies tend to reinvest all of their available capital back into their businesses rather than returning it to shareholders. Yet the WisdomTree ETF small-cap fund has found 750 different companies to include in this fund, and all told, a 30-day SEC yield of 3.44% shows that you can find dividend income from the smaller side of the U.S. stock universe.

The majority of the stocks in the portfolio are from the consumer discretionary, industrial, and real estate sectors. But you'll also find exposure to income-friendly businesses like financials and utilities, and even some higher-growth areas like technology make a representative showing in the ETF. Small-caps underperformed their larger counterparts in the U.S. market in 2017, and that makes a potential reversal in 2018 good cause to take a look at this small-cap oriented fund.

Picking a popular dividend index

Finally, any dividend investor knows that the Dividend Aristocrats are a good place to start to find blue chip stocks with good track records of paying their shareholders well. Dividend Aristocrats all boast a 25-year track record of growing payouts, and just over 50 stocks meet that test within the S&P 500. To get them, you'll have to go to ProShares S&P 500 Dividend Aristocrats ETF, which is the only fund to license the index from S&P Dow Jones Indices.

Among the fund's stocks, you'll find heavy concentrations in consumer, industrial, and healthcare stocks, with good helpings of materials and financial companies, as well. Dividend Aristocrats don't always have the highest yields, and that's why the dividend yield on the ETF is just 2.42%. Yet that's still above the market's overall average, and dividend investors have to appreciate the broad-based exposure that they get even from a relatively small number of stocks compared to other dividend ETFs in the space.

Pick the top dividend ETFs for 2018

Looking at the trends that could define 2018, a greater focus on non-U.S. stocks justifies a look at international ETFs like Vanguard International Dividend Appreciation. Incorporating small-cap exposure through the WisdomTree fund makes sense, while sticking with the tried-and-true returns of Dividend Aristocrats shows the value of the ProShares fund. Combining these three ETFs could make a big difference to your dividend investing portfolio in 2018 and beyond.

Dan Caplinger has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.