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We know we're not the only ones with burning investment questions that we're dying to have answered this year. So we asked three of our top Motley Fool contributors to share the investing question they would most like to see answered in 2015. 

Dan Caplinger
What I want to know most is whether this will finally be the year the stock market experiences a substantial correction. The 6-year-old bull market has been extraordinary not only because of its impressive gains but also because of how smooth the upward trend has been. Historically, investors could expect 5% mini-corrections about three times a year, with a larger 10% correction every year or so and a 20% decline about every three to four years. Yet the market has not experienced a 10% drop since 2011, and even the smaller 5% corrections have been much rarer in recent years than they were in the past.

Some signs of rising volatility have emerged over the past few months, with the huge plunge in oil prices creating massive pullbacks in energy stocks. Yet other areas of the market, such as transportation and utility stocks, have benefited from lower fuel costs, so the overall impact of oil's drop has not been negative to the market as a whole. With European central bankers now following the Federal Reserve's previous path of quantitative easing, it's conceivable the trend of a correction-free market will continue through another year.

Dan Dzombak
My question for 2015 is what the effect of low, zero, and negative interest rates around the world will be.

Globally, people are giving money to governments and central banks at the lowest levels in history. In the U.S., rates are between 0% and 0.25%; in the European Union, they're 0.05% to 0.3%; in the U.K. they're 0.5%; and in Japan they're 0%. Remarkably, two countries have gone so far as to implement negative interest rates, actually charging savers for funds deposited in banks. This month, Switzerland lowered its interest rate from -0.25% to -0.75%, while Denmark lowered its interest rate from -0.2% to -0.35%.

At the same time, central banks have been purchasing long-term assets to push down long-term interest rates. Central banks hope that by lowering interest rates, they can lower the returns on savings so that people and companies will invest in the real economy. The problem is that this seems to be pushing up financial markets while doing little to spur the real economy.

So, to be more specific, my questions are:

  1. What weaknesses in the system are being allowed to fester by holding interest rates near zero for so long?
  2. What will happen to the financial system given negative interest rates?

Compared to a negative interest rate from the bank, any positive return from stocks seems like a good deal. But are those returns founded, or are you just setting yourself up for the next financial crisis? 

Leo Sun
My biggest question for 2015 is how plunging oil prices will impact the global economy.

Although the energy sector will obviously be dragged down by low oil prices, other sectors could benefit. Retail spending could rise as consumers save more money at the pump. Homebuilders could post higher margins as construction costs decline. Airlines will likely post higher profits, as fuel costs are traditionally their No. 1 expense.

Low oil prices will also cause countries that are heavily dependent on the oil sector, such as Russia and Venezuela, to suffer. They could also cause some emerging markets with high debt but lots of oil -- Ecuador, for example -- to borrow more money from China, which could greatly boost China's sphere of influence.

Low oil prices could also backfire in certain ways. A top concern is deflation, in which plunging oil prices cause consumer prices to fall so quickly that people delay purchases to wait for better deals. Fewer purchases could hit corporate profits, which might lead to reduced hiring and wages.

I plan to keep a close eye on this marketwide balancing act in 2015. Oil prices won't fall forever, and well-informed investors should understand how those prices can affect their portfolios, even if they don't own any oil stocks.