Apple (AAPL) and NVIDIA (NVDA) have repeatedly traded places as the world's most valuable company over the past two weeks. Apple first surpassed NVIDIA with a market capitalization of $4.88 trillion on July 17, after which NVIDIA briefly reclaimed the top spot, only to be overtaken by Apple again on July 27. Apple's market cap briefly touched $5 trillion on July 28, but its stock subsequently fell 7% to 8% in after-hours trading following the release of strong third-quarter earnings, due to weak guidance for the current quarter (revenue growth of 9%-11%, below Wall Street's expectation of 12%) and a downward revision in gross margin guidance. Apple CEO Tim Cook attributed this to rising memory costs and a shortage of chip manufacturing capacity.