WESTFIELD CAPITAL MANAGEMENT CO LP
"13F equity value" = market value of this filer's US-listed long equity positions only. It excludes cash, bonds, non-US and short positions, so it understates a fund's true assets under management — often by a lot.
13F holdings are disclosed ~45 days after quarter-end, and they never reveal when within the quarter a fund actually bought. So any 13F-based summary is structurally late and blurred — this applies to every fund, including this one.
We backtested copying it anyway. Buying this fund's new positions the day each filing went public, over 32 quarters, returned +3.0% per quarter — versus +2.7% per quarter from simply owning every 13F stock. It beat that baseline in only 50.0% of quarters (excess t = 1.30, not statistically significant). Its filings tell you what it bought — not what you should buy.
Quarterly compounding, invested quarters only · entry 47 days after quarter-end (when 13F data becomes public)
Top 20 holdings of 250 · 2026 Q1
| Ticker | Value | Weight | QoQ |
|---|---|---|---|
| NVDA | $1.1B | | ADD |
| ASND | $1.1B | | TRIM |
| FIX | $856M | | TRIM |
| AAPL | $795M | | TRIM |
| FTAI | $698M | | ADD |
| MSFT | $611M | | HOLD |
| GOOGL | $583M | | TRIM |
| HWM | $528M | | ADD |
| VRT | $482M | | TRIM |
| AMZN | $475M | | TRIM |
| AXON | $452M | | ADD |
| AVGO | $383M | | ADD |
| LLY | $335M | | ADD |
| TPR | $310M | | ADD |
| META | $301M | | TRIM |
| LPLA | $265M | | ADD |
| MKSI | $241M | | ADD |
| INSM | $240M | | ADD |
| PCVX | $212M | | ADD |
| RKLB | $204M | | ADD |
QoQ vs previous quarter's share count · NEW = new position · ADD/TRIM = ±2% shares · HOLD = unchanged.
New positions in 2026 Q1
Method & Limitations
Method: a "new position" = held this quarter, absent last quarter (options excluded; stocks with <50 prior holders excluded to filter spin-off artifacts). Entry 47 days after quarter-end — the first day the public could act on the filing. Benchmark = equal-weighted universe of all 13F-held stocks. Limitations: quarterly snapshots can't see intra-quarter trades; survivorship bias — funds that shut down are absent, which flatters the sample. Statistics, not advice.