Global stocks ended the month of May on a mixed note.
Asian stocks were mostly higher on Tuesday, with the Shanghai Composite Index surging 3.3 percent.
However, the S&P 500 fell 0.1 percent and the STOXX Europe 600 fell 0.8 percent.
Despite Tuesday's decline, the S&P 500 finished May with a 1.5 percent gain and is up 2.6 percent for 2016.
Tom Lee, founder of Fundstrat Global Advisors, told CNBC that "the stock market should have double-digit gains this year".
In contrast, BlackRock has downgraded US and European stocks to neutral, citing elevated US valuations and the higher probability of a midyear interest-rate increase by the Federal Reserve.
Daniel Fisher at Forbes wrote that huge losses during the financial crisis may have distorted the cyclically adjusted price-earnings (CAPE) ratio commonly used to measure valuation though.
However, according to John Hussman, it is not just CAPE but a variety of valuation measures, some better-correlated with market returns, that show that we are now in "a situation from which no resolution is possible other than 0-2% investment returns on a 10-12 year horizon, and a market collapse over the completion of the current market cycle".