Exchange-traded funds offer a convenient way to invest in sectors or niches that interest you. If you expect technology-heavy companies to thrive over time as new products are developed and our growing and developing populations demand them, the Technology Select Sector SPDR ETF (NYSE: XLK) could save you a lot of trouble. Instead of trying to figure out which companies will perform best, you can use this ETF to invest in lots of them simultaneously.

The basics
ETFs often sport lower expense ratios than their mutual fund cousins. The technology ETF's expense ratio -- its annual fee -- is a very low 0.18%.

This ETF has performed rather well, outpacing the world market over the past three, five, and 10 years. As with most investments, of course, we can't expect outstanding performances in every quarter or year. Investors with conviction need to wait for their holdings to deliver.

With a low turnover rate of 5%, this fund isn't frantically and frequently rejiggering its holdings, as many funds do.

What's in it?
More than a handful of technology-oriented companies had strong performances over the past year. Data storage giant EMC (NYSE: EMC), for example, soared 22%. Among other initiatives, it's expanding into flash storage technology, and some have suggested that if it doesn't succeed quickly there, it might just acquire a competitor in order to not be left behind. It has partnered with Lenovo to serve China, too. Its management recently noted, "We believe we have the right strategy in place to leverage the 3 major waves of change in IT: cloud, Big Data and trust." Bulls also like its majority ownership of cloud computing specialist VMware, with some wondering whether the cash-rich company might start paying a dividend soon.

Other companies didn't do quite as well last year, but could see their fortunes change in the coming years. Corning (NYSE: GLW), for example, lost 18%. But Corning has a lot to recommend it, such as its very successful Gorilla Glass, embedded in many mobile devices (which are exploding in popularity). Weak demand for its LCD offerings has hurt Corning, but LCD television sales are expected to pick up. Meanwhile, the company is also a major fiber provider for growing networks, its revenue growth is picking up, and patient investors can collect a 2.6% dividend yield.

Broadcom (Nasdaq: BRCM), up 5%, is making some smart acquisitions that can boost its presence in mobile computing. Its products are found in many iDevices, which bodes well for its future performance. The company has recently been making deals to get into inexpensive Chinese smartphones, hoping to benefit from China's brisk growth. Some see the stock as a bargain right now.

Cognizant Technology Solutions (Nasdaq: CTSH), a specialist in IT consulting and outsourcing, gained 6%, but its revenue and earnings have been growing at a healthy clip. The company is building its consulting business, and recently upped its projections. It sports solid 14% net profit margins and little debt and is growing internationally.

The big picture
Demand for technology isn't going away anytime soon. A well-chosen ETF can grant you instant diversification across any industry or group of companies -- and make investing in and profiting from it that much easier.

If you're intrigued by Corning (and you should be), check out our new premium research report on it. Our analysts have jam-packed this report with the opportunities and threats that could cause Corning to rise or fall, and the report comes with a full year of updates.

Longtime Fool contributor Selena Maranjian, whom you can follow on Twitter, owns shares of Corning, but she holds no other position in any company mentioned. Click here to see her holdings and a short bio. Motley Fool newsletter services have recommended buying shares of Corning. The Motley Fool has a disclosure policy.

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