> ## Documentation Index
> Fetch the complete documentation index at: https://docs.exponent.finance/llms.txt
> Use this file to discover all available pages before exploring further.

# Calculate Global Fee Rate

> Calculate the global fee rate and TVL metrics between two market snapshots

The `MarketThree.calcGlobalFeeRate()` static method calculates the global fee rate and total value locked (TVL) metrics by comparing two market snapshots taken at different times.

## Usage

```typescript theme={null}
import { MarketThree } from "@exponent-labs/exponent-sdk";

// Create market snapshot data from historical and current state
const marketSnapshotCurrent = {
  syExchangeRate: 1.02,
  currentSpotPrice: 1.08,
  financials: currentFinancials,
  feeGrowthIndexGlobalPt: 1000000n,
  feeGrowthIndexGlobalSy: 2000000n,
  currentPrefixSum: 5000000n,
  snapshotTimeUnix: Math.floor(Date.now() / 1000),
};

const marketSnapshotHistory = {
  syExchangeRate: 1.01,
  currentSpotPrice: 1.07,
  financials: historicalFinancials,
  feeGrowthIndexGlobalPt: 900000n,
  feeGrowthIndexGlobalSy: 1800000n,
  currentPrefixSum: 4800000n,
  snapshotTimeUnix: Math.floor(Date.now() / 1000) - 86400, // 24 hours ago
};

const feeMetrics = MarketThree.calcGlobalFeeRate(
  marketSnapshotCurrent,
  marketSnapshotHistory
);

console.log("Total fee rate:", feeMetrics.totalFeeRate);
console.log("Total fees (base token):", feeMetrics.totalFeesInBaseToken);
console.log("TVL (base token):", feeMetrics.tvlInBaseToken);
```

## Parameters

| Parameter                   | Type                 | Required | Description                                    |
| --------------------------- | -------------------- | -------- | ---------------------------------------------- |
| `marketSnapshotDataCurrent` | `MarketSnapshotData` | Yes      | Current market snapshot data                   |
| `marketSnapshotDataHistory` | `MarketSnapshotData` | Yes      | Historical market snapshot data for comparison |

### MarketSnapshotData Type

```typescript theme={null}
{
  syExchangeRate: number;              // Current SY exchange rate
  currentSpotPrice: number;            // Spot price in format of 1 + percentage / 100
  financials: MarketThreeFinancials;   // Market financial data
  feeGrowthIndexGlobalPt: bigint;      // Global PT fee growth index
  feeGrowthIndexGlobalSy: bigint;      // Global SY fee growth index
  currentPrefixSum: bigint;            // Current prefix sum
  snapshotTimeUnix: number;            // Snapshot timestamp in Unix seconds
}
```

## Returns

Returns an object with:

```typescript theme={null}
{
  totalFeeRate: number;
  totalFeesInBaseToken: number;
  tvlInBaseToken: number;
}
```

| Property               | Type     | Description                                                |
| ---------------------- | -------- | ---------------------------------------------------------- |
| `totalFeeRate`         | `number` | The calculated fee rate (total fees / TVL)                 |
| `totalFeesInBaseToken` | `number` | Total fees earned in base token terms (PT + SY combined)   |
| `tvlInBaseToken`       | `number` | Total value locked in base token terms (PT + SY liquidity) |

## Calculation Details

The method performs the following calculations:

1. **Calculate PT fees in base token**:
   ```
   feePt = (feeGrowthPtCurrent - feeGrowthPtHistory) / currentPrefixSum
   feePtInBaseToken = feePt * ptPriceInBaseToken
   ```

2. **Calculate SY fees in base token**:
   ```
   feeSy = (feeGrowthSyCurrent - feeGrowthSyHistory) / currentPrefixSum
   feeSyInBaseToken = feeSy * syExchangeRate
   ```

3. **Calculate TVL**:
   ```
   ptLiquidity = ptBalance * ptPriceInBaseToken
   syLiquidity = syBalance * syExchangeRate
   tvl = ptLiquidity + syLiquidity
   ```

4. **Calculate total fee rate**:
   ```
   totalFeeRate = totalFeesInBaseToken / tvlInBaseToken
   ```

The PT price is calculated using time decay based on the time remaining until market expiration.