sem-ecommerce-metrics

# SEM & Ecommerce Metrics Reference

This skill provides domain knowledge for Search Engine Marketing (SEM), paid social, and ecommerce analytics. Use this to understand how metrics flow from ad platforms through analytics to business outcomes.

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## Core Data Sources

### Product Feed (Merchant Center / Catalog)

The master product catalog containing:

| Field | Description | Use |
|-------|-------------|-----|
| `g_id` / `id` | Variant ID (SKU) | Unique identifier per size/color |
| `g_item_group_id` | Product ID | Groups variants together |
| `g_title` | Product title | Display name |
| `g_price` | Price | Current selling price |
| `g_sale_price` | Sale price | Discounted price (optional) |
| `g_availability` | Stock status | "in_stock" or "out_of_stock" |
| `g_brand` | Brand name | Filtering/segmentation |
| `g_product_type` | Category path | Taxonomy |
| `g_custom_label_*` | Custom labels (0-4) | Campaign segmentation |

**Key Concepts**:
- **Variant vs Product**: One product (shoes) has many variants (sizes)
- **item_group_id**: Groups all variants of same product
- **Custom Labels**: Used to segment products in ad campaigns

### Google Analytics 4 (GA4)

User behavior and conversion data:

| Metric | Description | Aggregation |
|--------|-------------|-------------|
| `itemRevenue` | Revenue attributed to item | SUM |
| `itemPurchaseQuantity` | Units sold | SUM |
| `itemsViewed` | Product detail page views | SUM |
| `itemsAddedToCart` | Add to cart events | SUM |
| `itemsCheckedOut` | Checkout initiations | SUM |

**Key Concepts**:
- **Attribution**: Revenue attributed to last-click item
- **Item ID matching**: GA4 uses `item_id` field
- **Aggregated "(other)"**: Low-volume items grouped together
- **Data freshness**: 7-day refresh window

### Google Ads

Ad performance and cost data:

| Metric | Description | Aggregation |
|--------|-------------|-------------|
| `Cost` | Ad spend | SUM |
| `Clicks` | Ad clicks | SUM |
| `Impressions` | Ad impressions | S