← All S&P MidCap 400 additions
MP — S&P 400 index addition
MP Materials
Sector
Unknown
Announced
Sep 22, 2025
Effective
Sep 22, 2025
Replaced
Acadia Healthcare
1W after inclusion
-6.9%
-7.2% vs S&P 400
1M after inclusion
-4.7%
-4.4% vs S&P 400
3M after inclusion
-26.3%
-28.6% vs S&P 400
6M after inclusion
-30.9%
-38.0% vs S&P 400
1Y after inclusion
—
window not elapsed
Indexed performance around the effective date (effective close = 100)
Prices last updated: 2026-09-16 06:30 UTC (9h ago)
Run-up in the 30 days into inclusion: +7.9%
Other stocks added to the S&P MidCap 400
- SUI — Sun Communities joined on Aug 20, 2026.
- KRYS — Krystal Biotech joined on Jul 24, 2026.
- MOH — Molina Healthcare joined on Jul 22, 2026.
- BTSG — BrightSpring Health Services joined on Jul 17, 2026.
- ALSN — Allison Transmission joined on Jul 6, 2026.
- TOST — Toast, Inc. joined on Jul 1, 2026.
See the full S&P MidCap 400 additions log or the index review calendar.