Core USD Liquidity Index

### 🏦 Core USD Liquidity Index (v1)
**Purpose:**
The *Core USD Liquidity Index* tracks global **USD liquidity conditions**, the single most important macro driver behind risk-on and risk-off environments.

It combines 4 key monetary metrics into one normalized composite line:
- **FRED:RRPONTSYD** → Reverse Repo balance (⬆️ = liquidity tightening)
- **FRED:WALCL** → Federal Reserve balance sheet (⬆️ = liquidity expansion)
- **FRED:TB3MS** → 3-Month Treasury Bill rate (⬆️ = liquidity tightening)
- **TVC:DXY** → U.S. Dollar Index (⬆️ = global liquidity tightening)

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### 🧭 **How it Works**
Each metric is normalized and aggregated to create a unified liquidity signal.
The index functions as a **"Liquidity Thermometer"**, visualizing whether dollars are entering or leaving global financial circulation.

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### 📊 **Interpretation**
| Zone | Meaning | Market Behavior |
|------|----------|-----------------|
| 🟢 Above 0 | Liquidity expanding | Risk assets (BTC, SPX, Tech) strengthen |
| ⚪ Around 0 | Neutral liquidity | Sideways / indecisive markets |
| 🔴 Below 0 | Liquidity contracting | USD strengthens, risk assets weaken |

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### 💡 **Use Cases**
- Identify **macro liquidity inflection points** ahead of price action
- Track **Fed policy impact** (balance sheet, RRP flows, T-Bill yields)
- Confirm or fade BTC/SPX rallies based on liquidity context

**Recommended timeframe:** Weekly or Daily
**Best pairs:** BTCUSD, SPX500, NASDAQ100, XAUUSD