(Bloomberg) — Worries have been mounting for weeks that the S&P 500’s (^GSPC) push to record after record risks becoming a bubble, with the index’s swollen valuation cited most often as cause for concern. Critics point to the tech sector’s outsize influence on this year’s gain, with just five stocks, all megacap tech firms, driving half of the 12% advance. But a closer look shows tech giants have largely justified their elevated valuations with profit growth that outstrips share-price appreciation. Most ...