etf-premium

这段内容是审核时保存的快照。外部来源才是完整且最新的版本。

---
name: etf-premium
description: >
  Calculate ETF premium/discount vs NAV via Yahoo Finance, and decompose single-day surges
  into NAV-driven vs structural components (gamma squeeze, dealer hedging, blocked AP arbitrage).
  Use whenever the user asks about an ETF's premium or discount, NAV comparison, why an ETF
  diverged from its holdings, or how much of a move is dealer-hedging-driven.
  Triggers: "ETF premium", "ETF discount", "NAV premium", "is SPY at a premium", "BITO premium",
  "IBIT premium", "bond ETF discount", "trading above/below NAV", "ETF premium screener",
  "biggest discount", "compare ETF NAV", "ETF arbitrage", "ETF gamma squeeze",
  "ETF premium surge", "decompose ETF move", "dealer gamma exposure", "GEX for ETF",
  "why did this ETF jump", "premium convergence", "AP arbitrage blocked", or any request
  about the gap between an ETF's price and underlying value. Especially relevant for
  leveraged, inverse, international, bond, commodity, and crypto ETFs.
---

# ETF Premium/Discount Analysis Skill

Calculates the premium or discount of an ETF's market price relative to its Net Asset Value (NAV) using data from Yahoo Finance via [yfinance](https://github.com/ranaroussi/yfinance).

**Why this matters:** An ETF's market price can diverge from the value of its underlying holdings (NAV). When you buy at a premium, you're overpaying relative to the assets; at a discount, you're getting a bargain. This divergence is typically small for liquid US equity ETFs but can be significant for bond ETFs, international ETFs, leveraged/inverse products, and crypto ETFs — especially during periods of market stress.

**Important**: For research and educational purposes only. Not financial advice. yfinance is not affiliated with Yahoo, Inc.

---

## Step 1: Ensure Dependencies Are Available

**Current environment status:**

```
!`python3 -c "import yfinance, pandas, numpy; print(f'yfinance={yfinance.__version__} pandas={pandas.__version__} numpy={numpy.__version__}')" 2>/dev/null || echo "DEPS_MISSING"`
```

If `DEPS_MISSING`, install required packages:

```python
import subprocess, sys
subprocess.check_call([sys.executable, "-m", "pip", "install", "-q", "yfinance", "pandas", "numpy"])
```

If already installed, skip and proceed.

---

## Step 2: Route to the Correct Sub-Skill

Classify the user's request and jump to the matching section. If the user asks a general question about an ETF's premium or discount without specifying a particular analysis type, default to **Sub-Skill A** (Single ETF Snapshot).

| User Request | Route To | Examples |
|---|---|---|
| Single ETF premium/discount | **Sub-Skill A: Single ETF Snapshot** | "is SPY at a premium?", "AGG premium to NAV", "BITO premium" |
| Compare multiple ETFs | **Sub-Skill B: Multi-ETF Comparison** | "compare bond ETF discounts", "which has bigger premium IBIT or BITO", "rank these ETFs by premium" |
| Screener / find extreme premiums | **Sub-Skill C: Premium Screener** | "which ETFs have biggest discount", "find ETFs trading below NAV", "premium screener" |
| Deep analysis with context | **Sub-Skill D: Premium Deep Dive** | "why is HYG at a discount", "is ARKK premium normal", "ETF premium analysis with context" |
| Sudden premium surge / gamma squeeze | **Sub-Skill E: Premium Surge Decomposition** | "why did KWEB jump 13% today", "is this ETF rally driven by gamma", "decompose today's ETF move", "dealer GEX for SOXL", "how long until the premium converges" |

### Defaults

| Parameter | Default |
|---|---|
| Data source | yfinance `navPrice` field |
| Price field | `regularMarketPrice` (falls back to `previousClose`) |
| Screener universe | Common ETF list by category (see Sub-Skill C) |

---

## Sub-Skill A: Single ETF Snapshot

**Goal**: Show the current premium/discount for one ETF with context about what's normal, plus a peer comparison to show how it stacks up against similar ETFs.

### A1: Fetch and compute

```python
import yfinance as yf

# Peer groups by category