run2-13f-holdings-comparison

name	run2_13f-holdings-comparison
description	How to accurately identify stocks that "received increased investment" by checking both share count and dollar value change.

Overview

To determine if a fund truly invested more in a stock (rather than the stock simply going up in price), you must check if their total share count (SSHPRNAMT) increased.

Usage Patterns

Identifying True Buys

This script compares Q2 and Q3 data to find stocks where the manager actively purchased more shares (SHARE_CHANGE > 0), and ranks them by the total change in reported dollar value (VALUE_CHANGE).

import pandas as pd

q2_acc = "0000950123-25-008343"
q3_acc = "0001193125-25-282901"

q2_info = pd.read_csv("/root/2025-q2/INFOTABLE.tsv", sep="\t", dtype=str)
q3_info = pd.read_csv("/root/2025-q3/INFOTABLE.tsv", sep="\t", dtype=str)

holdings_q2 = q2_info[q2_info["ACCESSION_NUMBER"] == q2_acc].copy()
holdings_q3 = q3_info[q3_info["ACCESSION_NUMBER"] == q3_acc].copy()

# Ensure numeric types
holdings_q2["SSHPRNAMT"] = holdings_q2["SSHPRNAMT"].astype(float)
holdings_q3["SSHPRNAMT"] = holdings_q3["SSHPRNAMT"].astype(float)
holdings_q2["VALUE"] = holdings_q2["VALUE"].astype(float)
holdings_q3["VALUE"] = holdings_q3["VALUE"].astype(float)

# Group by CUSIP to handle multiple lines per stock
sum_q2 = holdings_q2.groupby("CUSIP")[["SSHPRNAMT", "VALUE"]].sum().reset_index()
sum_q3 = holdings_q3.groupby("CUSIP")[["SSHPRNAMT", "VALUE"]].sum().reset_index()

# Merge and calculate changes
merged = pd.merge(sum_q2, sum_q3, on="CUSIP", how="outer", suffixes=("_q2", "_q3")).fillna(0)
merged["SHARE_CHANGE"] = merged["SSHPRNAMT_q3"] - merged["SSHPRNAMT_q2"]
merged["VALUE_CHANGE"] = merged["VALUE_q3"] - merged["VALUE_q2"]

# Filter for stocks where the manager actually purchased more shares
increased_shares = merged[merged["SHARE_CHANGE"] > 0]

# Rank by Dollar Value Increase
top_5 = increased_shares.sort_values(by="VALUE_CHANGE", ascending=False).head(5)
print(top_5[["CUSIP", "SHARE_CHANGE", "VALUE_CHANGE"]])