As for the currently surging U.S. tech stocks, it's premature to fret about the presence of a bubble. Peter Oppenheimer, a strategist at Goldman Sachs Group, holds the view that the unprecedented spike in the share prices of tech behemoths has been underpinned by solid earnings growth. In contrast, past market rallies during bubble eras were mainly fueled by speculative activities. Oppenheimer and his team emphasized in the report: "While the valuations of the tech sector are gradually climbing to elevated levels, they haven't yet hit the extremes witnessed during historical bubble periods."