Concerns over iPhone sales have led to a 4% decline in Apple's stock in 2024, putting it at risk of losing its title as the world's most valuable company to Microsoft. Apple's market cap is now at $2.866 trillion, compared to Microsoft's $2.837 trillion. iPhone sales in China dropped 30%, adding to competitive pressures from local rivals. Apple's Vision Pro mixed-reality headset sales commence on Feb. 2, but UBS estimates minimal impact on 2024 earnings. Both Apple and Microsoft have relatively high price-to-earnings ratios. Apple's forward PE is 28, while Microsoft trades at around 31 times forward earnings. Apple's recent sales forecast miss and weak demand for iPads and wearables contribute to the stock dip. Microsoft, with an expected 16% revenue increase, may pose a challenge to Apple's valuation supremacy. Apple reports results on Feb. 1, while Microsoft's report is forthcoming.