The term is slightly out of date, since Facebook became Meta and Google became Alphabet, but the concept is unchanged. In many different contexts from Stock Analysis though Market Share on to Business Models, comparisons are made between the Big Five High Tech Companies: Google (Alphabet), Apple, Facebook (Meta), Amazon and Microsoft.
The acronym, coined by Goldman Sachs, includes these companies for two reasons. First of all, the big five tech companies make up as much as 13% of the value of the whole S&P 500 by market capitalization. Second, those are the leading companies that bring sociocultural evolution at a big scale and drive social change at full speed.
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