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

# Affected Event Count: Events Impacted by EMQ Issues

> Track how many events are impacted by Meta EMQ diagnostic issues. Identify scale of data quality problems affecting your conversion matching.

<Tip>
  Affected Event Count shows the number of events impacted by a specific EMQ diagnostic issue, helping you understand the scale of data quality problems.
</Tip>

## Formula

<Info>
  **Affected Event Count** = **COUNT** ( Events ) **WHERE** diagnostic\_issue = active
</Info>

### Formula Components

| Metric                                                                     | Definition                                                             |
| -------------------------------------------------------------------------- | ---------------------------------------------------------------------- |
| **Events**                                                                 | Total events sent via Conversions API                                  |
| [**diagnostic\_issue = active**](/data-dictionary/measures-and-dimensions) | Filters to events with a specific data quality problem flagged by Meta |

| Metadata        |                                   |
| --------------- | --------------------------------- |
| **Type**        | Number                            |
| **Data Source** | [Meta Ads](/sources/facebook-ads) |
| **Aggregation** | Count                             |

***

## Example

Your Purchase event has a diagnostic issue flagged for **missing phone numbers**:

| Event Type  | Total Events | Affected Events | Impact         |
| ----------- | ------------ | --------------- | -------------- |
| Purchase    | 12,450       | 3,847           | 30.9% affected |
| AddToCart   | 45,200       | 8,104           | 17.9% affected |
| ViewContent | 128,000      | 15,360          | 12.0% affected |

***

## How It Works

Meta's Event Match Quality system scans your Conversions API events for data quality issues. Each diagnostic issue tracks how many events are impacted. Higher counts indicate a broader problem that affects more of your conversion data and may reduce attribution accuracy.

***

## When to Use

| Scenario              | Action                                                   |
| --------------------- | -------------------------------------------------------- |
| Prioritizing fixes    | Focus on diagnostics affecting the most events first     |
| Measuring improvement | Track affected count over time after implementing fixes  |
| Assessing impact      | Understand how widespread a specific data issue is       |
| Resource allocation   | Allocate engineering time based on event volume affected |

***

## Related Metrics

| Metric                                                                              | Relationship                             |
| ----------------------------------------------------------------------------------- | ---------------------------------------- |
| [Affected Events %](/reference/metrics/data-quality/emq/affected-events-percentage) | Percentage version of this metric        |
| [Diagnostics Count](/reference/metrics/data-quality/emq/diagnostics-count)          | Total number of active diagnostic issues |

[See all EMQ metrics →](/reference/metrics/data-quality/emq)