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Vic Chen
Vic Chen

Posted on • Originally published at 13finsight.com

How to Compare Two 13F Filings Side by Side — The Framework That Actually Works

#investing #finance #data #beginners

A single 13F filing is a snapshot. Two consecutive filings are a story. The comparison between quarters is where the real insight lives.

Here's a systematic framework for comparing 13F filings that surfaces actionable signals instead of noise.

What to compare

When you put two quarterly filings side by side, focus on five dimensions:

1. New positions (entries)

Stocks that appear in Q4 but weren't in Q3. These are fresh conviction.

Signal strength depends on:

  • Size of the initial position (>1% of portfolio = strong conviction)
  • Whether the stock is in the manager's usual sector (in-sector = research-driven, out-of-sector = thesis shift)
  • Whether multiple watched managers entered the same name

2. Exits (complete sells)

Stocks that were in Q3 but gone in Q4. Complete exits are louder than trims.

What to investigate:

  • Did the stock perform poorly between quarters? (stop-loss)
  • Did the thesis change? (fundamental re-evaluation)
  • Did multiple managers exit the same name? (consensus abandonment)

3. Significant size changes

Positions that grew or shrank by >25% in share count.

Adding >25%: The manager is doubling down. Especially meaningful if the stock dropped between quarters (buying the dip = conviction).

Trimming >25%: Taking profits or reducing risk. Check if the stock rallied between quarters (selling strength) or if the trim coincides with a sector rotation.

4. Concentration changes

Compare top-5 and top-10 weights between quarters.

Change What it signals
Concentration increasing Rising conviction in fewer names
Concentration decreasing Hedging, uncertainty, or forced diversification
Top names reshuffled Active rebalancing, changing thesis
Top names unchanged Steady conviction, buy-and-hold approach

5. Sector weight shifts

Aggregate holdings by sector and compare weights.

  • Tech weight up, healthcare weight down = growth rotation
  • Financials weight up, tech weight down = value/rate rotation
  • Energy weight appearing = macro/inflation hedge
  • Defensive sectors growing = risk-off positioning

The comparison template

For each manager comparison, fill in:

Manager: [Name]
Q3 → Q4 comparison

NEW POSITIONS (top 3 by size):
1. [Ticker] - [$ value] - [% of portfolio]
2. ...
3. ...

EXITS (top 3 by former size):
1. [Ticker] - [former % of portfolio]
2. ...
3. ...

SIGNIFICANT INCREASES (>25%):
1. [Ticker] - [old shares → new shares] - [% change]

SIGNIFICANT DECREASES (>25%):
1. [Ticker] - [old shares → new shares] - [% change]

CONCENTRATION:
Top-5: [Q3 %] → [Q4 %]
Top-10: [Q3 %] → [Q4 %]

SECTOR SHIFTS:
[Sector up] / [Sector down]
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Cross-manager comparison

The most powerful analysis isn't comparing one manager across quarters — it's comparing multiple managers in the same quarter.

The convergence matrix

Create a simple matrix:

           | Manager A | Manager B | Manager C | Manager D |
-----------|-----------|-----------|-----------|-----------|
NVDA       | +50%      | NEW       | unchanged | -20%      |
AAPL       | -30%      | unchanged | EXIT      | unchanged |
TSLA       | NEW       | +25%      | NEW       | unchanged |
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Patterns that emerge:

  • NVDA: Mixed signals (A adding, D trimming) — no consensus
  • AAPL: Negative trend (A trimming, C exiting) — weakening conviction
  • TSLA: Emerging interest (A and C both new) — possible consensus forming

Common comparison mistakes

  1. Ignoring share splits and corporate actions: A position that "doubled" might just reflect a 2:1 split
  2. Comparing dollar values without adjusting for price changes: A position worth $1B that's now worth $1.2B might have fewer shares (the manager trimmed but the stock rose)
  3. Treating passive and active managers the same: Vanguard's changes are mostly index-driven, not conviction-driven
  4. Over-interpreting small changes: A 5% trim in a 0.3% position is noise
  5. Ignoring the amendment cycle: The Q3 filing you're comparing to might have been amended since you last checked

Tools and automation

For systematic comparison, you need:

  • Historical filing data (not just current quarter)
  • Share count AND dollar value for each position
  • Sector classification for each holding
  • A way to flag new entries, exits, and significant changes automatically

This is exactly what 13F Insight's quarter-over-quarter comparison tools are built for — surfacing the changes that matter without manually diffing XML files.

Originally published at 13F Insight

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