Tell us what you think: Which market storyline is bringing you down?

• Markets have had a strong start to 2018, with major indexes hitting record highs in the first two weeks of the year
• Still, some remain concerned about low U.S. inflation and the end of the bull run in bond markets

Pedestrians walk past the London Stock Exchange Group's offices in London, U.K., on Tuesday, May 30, 2017.

Simon Dawson | Bloomberg | Getty Images

Markets around the world have had a strong start to the year, with many major indexes notching new all-time highs, as investors bet on continued global growth.

U.S. stocks rose to record levels last Friday, with the positive sentiment also seen in other major markets: The pan-European was within sight of its all-time high of 415.18 and MSCI's broad index of shares in Asia Pacific excluding Japan touched a fresh record high on Monday.

But amid the optimism, some investors also have an eye on potential causes for concern, including the end of the bull run for bonds and persistent low volatility in markets. Others are convinced that the Federal Reserve is unlikely to hit its 2 percent inflation target this year as low U.S. inflation is set to continue.