**The population of Silicon Valley has slightly decreased over the last 10 years (2015–2025).**
Silicon Valley typically refers to Santa Clara and San Mateo Counties in California (sometimes including parts of nearby areas, but core data focuses here). According to the Silicon Valley Index and U.S. Census data:
- In 2015, the combined population was about 3,000,000 (reaching this milestone that year).
- By 2023, it had fallen to roughly 2,993,000, a decline of 0.2% from 2013 levels (adjusted for the decade).
- Projections for 2025 estimate around 2,983,000–2,990,000, continuing the slight downward trend due to net domestic out-migration outweighing international immigration and natural growth.
Key drivers include high housing costs pushing out residents, declining birth rates (down 34% since 1992, with a 2% drop in 2024), and an aging population (65+ up 28% since 2013, while under-18 fell 14%). The overall change is small—under 1% net decrease—but marks a shift from earlier growth.