BLAIR WILLIAM & CO/IL CSGP — COSTAR GROUP INC COM COM

Ownership history in BLAIR WILLIAM & CO/IL  ·  89 quarters on record

AI Ownership Summary

BLAIR WILLIAM & CO/IL reported COSTAR GROUP INC COM COM (CSGP) in 89 quarterly 13F filings from 2023 Q4 through 2025 Q4. Peak portfolio weight reached 1.34% in 2024 Q1. The latest visible filing shows CSGP at 0.37% of the fund.

This page tracks quarterly shares, estimated market value, portfolio weight, filing dates, and disclosure-aligned stock prices directly from SEC EDGAR 13F filings. Older history is available after unlock; the visible window still shows the most recent pattern.

What this CSGP ownership page tells you

This page is designed to answer the real investor question behind a 13F filing: how meaningful was BLAIR WILLIAM & CO/IL's position in COSTAR GROUP INC COM COM, and how did that conviction change over time? You can read the holding window, peak weight, latest reported size, disclosure timing, and quarter-by-quarter changes without piecing the story together from raw SEC rows.

Freshest filing
Latest Reported Filing
2025 Q4

CSGP was reported at 0.37% of portfolio in the most recent visible filing.

High-water mark
Peak Conviction
1.34% in 2024 Q1

Peak weight helps separate a token disclosure from a real conviction holding the fund genuinely cared about.

Time in book
Holding Window
2023 Q4 to 2025 Q4

Longer holding windows often tell a very different story from short-lived tactical trades or one-quarter experiments.

Decision context
Why It Matters
Position size beats headlines

Knowing that a fund owned a stock is useful. Knowing whether it was a 0.20% placeholder or a true high-conviction position is where the signal actually starts.

CSGP stock page BLAIR WILLIAM & CO/IL fund profile BLAIR WILLIAM & CO/IL full holdings
How BLAIR WILLIAM & CO/IL held CSGP — position size vs. price
% of Fund (quarterly)    CSGP price (quarter-end, indexed to 100)    SPY (indexed to 100)    QQQ (indexed to 100)
📋 Quarterly Holdings History 9 quarters  ▾
Quarter Action Sold % After 3M Timing Shares Change Chg % % of Fund Mkt Value Filed Price (Filed)
2025 Q4 REDUCED 35.3% -40.0% ✅ 2,023,523 -1,104,950 -35.3% 0.37% $136.1M 2026-02-14 (Est.) $44.99
2025 Q3 ADDED — — — 3,128,473 +257,311 +9.0% 0.70% $263.9M 2025-11-12 $69.02
2025 Q2 REDUCED — — — 2,871,162 -32,356 -1.1% 0.64% $230.8M 2025-07-24 $92.96
2025 Q1 REDUCED 14.5% +1.5% ❌ 2,903,518 -490,433 -14.5% 0.69% $230.0M 2025-05-09 $74.57
2024 Q4 REDUCED 11.9% +10.7% ❌ 3,393,951 -456,885 -11.9% 0.71% $243.0M 2025-02-12 $73.27
2024 Q3 REDUCED 12.4% -4.8% ✅ 3,850,836 -546,902 -12.4% 0.85% $290.5M 2024-11-12 $75.41
2024 Q2 REDUCED — — — 4,397,738 -22,040 -0.5% 1.01% $326.0M 2024-08-12 $72.03
2024 Q1 ADDED — — — 4,419,778 +26,800 +0.6% 1.34% $427.0M 2024-05-09 $91.34
2023 Q4 ADDED — — — 4,392,978 +201,969 +4.8% 1.31% $383.9M 2024-02-12 $82.88
80 older quarters hidden  —  Sign in free or upgrade to Premium to see full history

🏢 Other funds also holding CSGP

As of 2026 Q1 — sorted by position size

S.E.E.D. Planning Group LLC 3Y 2.57% RIVERBRIDGE PARTNERS LLC 3Y 7Y 1.21% Chicago Capital, LLC 3Y 7Y 1.15% CORTLAND ASSOCIATES INC/MO 3Y 7Y 1.05% PEREGRINE CAPITAL MANAGEMENT LLC 3Y 7Y 1.05% LOUISBOURG INVESTMENTS INC. 1.02% Buttonwood Financial Advisors Inc. 3Y 0.87% Foster Victor Wealth Advisors, LLC 3Y 7Y 0.73% Pacific Capital Partners Ltd 0.69% Aurora Investment Managers, LLC. 3Y 0.66%

FAQ About BLAIR WILLIAM & CO/IL and CSGP

These are the practical questions this page is built to answer before you even open the full history table.

How long has BLAIR WILLIAM & CO/IL reported owning CSGP?

BLAIR WILLIAM & CO/IL reported CSGP across 9 quarterly 13F filings, from 2023 Q4 through 2025 Q4.

What was the largest reported CSGP position in BLAIR WILLIAM & CO/IL's portfolio?

The largest reported portfolio weight for CSGP was 1.34% in 2024 Q1.

What is the latest reported CSGP position on this page?

The most recent filing on this page is 2025 Q4, when BLAIR WILLIAM & CO/IL reported 2,023,523 shares, equal to 0.37% of portfolio, with an estimated market value of $136.1M.

What does the chart on this CSGP ownership page compare?

The chart compares BLAIR WILLIAM & CO/IL's quarterly CSGP portfolio weight with the stock's indexed share price, so you can see whether the fund was building, trimming, or holding the position as price moved.

How well did BLAIR WILLIAM & CO/IL time their CSGP position?

Based on 13F filing dates vs. subsequent CSGP price moves, BLAIR WILLIAM & CO/IL correctly timed 37 out of 88 reported position changes (42%). The annualised alpha on CSGP relative to SPY over the holding period was +1.3%.

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