The next 25 years could prove “far more interesting and more challenging” for investors than the past 25, according to Tobias Levkovich, chief US equity strategist at Citigroup.

“Near-record margins will be difficult to maintain over the next 25 years. Following a period in which corporate margins rebounded to levels not seen since the 1960s, it seems difficult to conceive that profit trends will be able to match the 1980s-1990s golden period of improvement. Thus stock market gains could become more muted,” he says.