Goldman Sachs CEO David Solomon says don't expect stocks to keep delivering double-digit returns, because the boom won't last forever

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• Don't expect stocks to keep delivering the bumper returns of the past few years, Goldman Sachs' CEO said.
• Double-digit equity returns can't be expected to compound in perpetuity, David Solomon told CNBC Tuesday.
• While Solomon believes in fintech, cryptos like bitcoin or ether don't matter to him personally.

Investors should expect lower returns in stocks over the next couple of years, because...