Is That 13F Manager Actually Picking Stocks? How to Tell in 30 Seconds

Not all 13F filers are stock pickers. Many are just tracking an index. Confusing the two will wreck your analysis. The Quick Test Three things to check: 1. Holding Count < 50 holdings : Almost certainly active 50-200 holdings : Could go either way — check concentration 500+ holdings : Probably passive or semi-passive 5000+ holdings : Definitely an index tracker (Vanguard, BlackRock, State Street) 2. Top-5 Concentration > 25% in top 5 : Active manager with conviction 15-25% in top 5 : Moderate — could be enhanced index < 15% in top 5 : Broad index exposure 3. Overlap With S&P 500 If a manager's top 10 looks exactly like the S&P 500 top 10 (AAPL, MSFT, NVDA, AMZN, GOOGL...), they're probably running index money. The signal is in the deviations from the benchmark, not the holdings themselves. Why This Matters Copying a passive manager's 13F is literally just buying the index with extra steps and a 45-day delay. The edge comes from identifying active managers with concentrated bets and tra