“The Shiller CAPE is at 30 times its historical average, which has been something like 16.8 times, so clearly that’s a concern,” Andrew told CNBC’s Street Signs on Thursday. “I think it’s been higher a couple of times previously.”

Andrew added: “The warning signs are flashing with regards to valuation but the key in valuations is not just the price, there are two sides to it – there’s the earnings (growth). If you look at the latest numbers, Q1 earnings rose by something like 15.5 percent, versus the S&P which did 5.5 percent in that quarter.”