Alphabet suffers $758 billion market-value loss in October, its biggest monthly decline

Alphabet Inc.'s stock experienced a sharp decline in October, shedding about $758 billion in market value, a loss that ranks as the second-largest monthly drop for any U.S.-listed company. The decline followed a week in which the company lost $468 billion, its worst weekly performance on record, after reporting third-quarter results that triggered a $475 billion drop in a single day.

The October slide represents a near 19% fall, the steepest monthly percentage decline since the company went public in 2004, surpassing the previous record 18.5% drop in November 2008. The week’s 13% decline was the worst since August 2011. The selloff pushed Alphabet's price-to-earnings ratio to its lowest level in more than a decade.

Other technology firms also saw sizable losses; SpaceX, Intel and Nvidia each lost over $100 billion in market value during the same week, while Intel fell as much as 30% after issuing a weak outlook. Conversely, companies such as Eli Lilly, Tesla and SK Hynix added more than $300 billion combined to market value.

"Further volatility does not make retreating from markets an effective way to protect portfolios from potential drawdowns, in our view," wrote Ulrike Hoffmann-Burchardi, chief investment officer for UBS's Americas and global equities team. "We continue to see scope for equity gains overall and believe investors should focus on building a resilient portfolio that includes exposure beyond tech."

Alphabet's October performance marks its worst month in both dollar and percentage terms since its initial public offering, ending the week only about $7 above the level needed to match Nvidia's record weekly loss.