Most investors concentrate on the best-known stocks in the market. But by looking beyond the ordinary run-of-the-mill companies that everybody knows about, you can find some insight on prevailing trends that you might otherwise never notice.

One little-followed niche investment is the closed-end fund. These predecessors to exchange-traded funds differ from traditional mutual funds in that they trade on stock exchanges throughout the market day. Yet unlike ETFs, they have only a fixed number of shares available, making the funds subject to supply and-demand pressures. As a result, you can tell which areas are hot and which are cold just by looking at whether investors are willing to pay a premium for shares compared to their net asset value, or whether buyers are only willing to pay a discounted price for shares.

Let's take a look at three interesting conclusions you can draw from the current state of the closed-end fund market.

Lesson 1: Income is king.
A look at the four funds trading at the highest premiums to net asset value reveals a common thread: They're all focused on maximizing income. What's interesting, though, is that they use different methods to reach the same ends. Among the three PIMCO funds, PIMCO High Income (NYSE:PHK) looks largely to the high-yield bond market for its holdings, while PIMCO Corporate & Income Opportunities (NYSE:PTY) has a somewhat lower distribution rate but has a sizable allocation to investment-grade debt. The fund with the highest premium, PIMCO Global StocksPLUS, uses futures contracts to add stock exposure to its portfolio of income-producing bonds. Finally, BlackRock Virginia Municipal Bond rounds out the top four with its tax-free bond portfolio.

With premiums ranging from 27% all the way up to 56%, investors are clearly willing to pay up for these funds' big distributions, even when their portfolios aren't able to generate enough actual investment income to cover what they pay out. It may seem inevitable that investors will figure out they're overpaying, but so far, those premiums have persisted for a long time without signs of disappearing.

Lesson 2: Leverage is plentiful.
All four of the closed-end funds above share another common trait: They all use leverage to boost their returns. By getting cheap financing and using the proceeds to buy higher-returning securities, closed-end funds can boost their investment returns.

That's the same strategy that has led to such strong gains for mortgage REIT Annaly Capital (NYSE:NLY). But like Annaly, these closed-ends rely on low borrowing rates to generate the spreads necessary to create bigger profits. If interest rates rise, the high leverage levels in closed-end funds may backfire.

Lesson 3: Europe is unloved, but is it a value?
On the other side of the popularity coin, looking at a list of funds trading at big discounts to their net asset value reveals many closed-ends that focus on Europe. With discounts of more than 10%, funds covering Switzerland, Ireland, Turkey, and Germany, as well as broader-based central and eastern European funds, have drawn little interest from investors lately.

You can see the same trends among many individual European stocks. Telecom giant Telefonica (NYSE:TEF) has big exposure to Latin America, but investors focus on its home country of Spain in limiting its gains. The same trend has affected French oil giant Total (NYSE:TOT), which shares the same exposure to energy projects around the world yet has been tarnished by its proximity to the crisis-ridden continent. By focusing on value rather than perception, you can get some great values when others are being irrational.

Don't stop searching
You may never decide to buy shares of a closed-end fund for your own portfolio, but that doesn't mean you shouldn't pay attention to the closed-end market. Studying various corners of the investment world can give you extra information compared to those who merely focus on the biggest headlines.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool recommends Total. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.