How to Compare Two 13F Filers Without Getting Fooled by AUM

Comparing two 13F filers by raw size alone usually produces the wrong conclusion. A $6 trillion filing can be more informative about market plumbing, while an $800 billion filing can tell you much more about conviction. Good comparison starts with AUM, but it does not stop there.

The Four Questions To Ask First

1. How concentrated is each portfolio?
2. How much changed this quarter?
3. Are the top holdings mostly ETFs, single stocks, or options?
4. What job is the portfolio trying to do?

Why AUM Alone Misleads

A huge filer may simply be a broad allocator or custodian-style institution. A smaller filer can still send a much stronger signal if the top positions are concentrated and the quarter-to-quarter changes are aggressive. Compare Oak Grove with Rehmann. Oak Grove says more about conviction because Micron and NVIDIA dominate the book. Rehmann says more about asset allocation because ETFs lead the filing and the growth overlay sits on top.

Use Concentration Before You Use Headlines

If one manager has a top-five weight above 60% and another has a top-five weight below 30%, they are not playing the same game. That is why concentration metrics matter so much on 13F Insight. They tell you whether the filing should be read like an allocator, a stock picker, or a tactical hedge book.

Then Look at Change, Not Just Size

Quarterly changes are often more informative than current size. Mariner added 65 new positions, which tells you it was actively rebuilding. Anchor kept a broad book but sharply increased specific growth exposures. Those are very different signals even if both filings are huge.

How To Compare Two Filers on 13F Insight

1. Open both filer detail pages.
2. Record top-1 and top-5 concentration.
3. Check new positions, exits, and the largest adds.
4. Note whether the core is stock-led, ETF-led, or option-led.
5. Only then decide which filing is more relevant to your own investing style.

Common Mistakes

• Mistake: Assuming the larger manager is smarter. Reality: Larger often just means broader.
• Mistake: Comparing position values without weights. Reality: Weight is what reveals conviction.
• Mistake: Ignoring whether the portfolio is ETF-heavy. Reality: ETF-heavy books are often about allocation, not stock selection.

FAQ

What is the best first comparison metric?

Top-five concentration. It quickly tells you what kind of portfolio you are dealing with.

Should I compare absolute dollar values or weights?

Start with weights. Dollar values alone can distort the picture.

How do I compare a broad ETF allocator with a concentrated stock picker?

Don't force them into the same frame. Compare them by purpose first, then by changes and concentration.

Why does turnover matter?

Because a filing with many new positions or exits is telling you more about the current quarter than a nearly static one.