Definition
Time-decay attribution is a multi-touch attribution model that assigns increasing credit to email interactions as they get closer in time to the conversion event. The most recent campaign receives the largest share of credit, the one before it receives less and so on, following an exponential or linear decay curve.
This model acknowledges that while earlier campaigns may have introduced a subscriber to the product, the campaigns closest to the purchase likely had the strongest influence. It offers a middle ground between last-touch attribution, which ignores early touchpoints, and linear attribution, which treats all touchpoints as equally influential.
How the Decay Curve Works
A typical time-decay model divides the conversion value across touchpoints using a half-life formula. If the half-life is set to seven days, a touchpoint seven days before conversion receives half the credit of one on the day of conversion. The decay rate and half-life window are configurable per business.
Best Practices
- Use time-decay attribution when your sales cycle is short to medium length
- Calibrate the half-life based on actual observed time-to-conversion data rather than guesswork
- Combine time-decay data with qualitative input from surveys or customer interviews to validate assumptions
- Compare results against last-touch and first-touch models to understand how attribution choice affects your conclusions
Related Glossary Terms
A/B Testing
A/B testing in email marketing is the practice of sending two variations of an email to a small sample of your list to determine which version performs better before sending the winner to the remaining subscribers.
ARPU (Average Revenue Per User)
ARPU (Average Revenue Per User) is a metric that measures the average revenue generated per email subscriber over a specific period, used to evaluate list value and campaign effectiveness.
Attention Rate
Attention rate is the percentage of email opens that last longer than 5 seconds, distinguishing genuine reads from passive opens, preview-pane views, or Apple MPP auto-loads.
Bounce Rate
Email bounce rate is the percentage of emails that were rejected by the receiving server before reaching the recipient. It is a key indicator of list health and data quality.
Campaign Internal Rate of Return (IRR)
Campaign IRR is the annualised return rate earned by an email campaign, accounting for the timing and magnitude of costs and revenue across the campaign's full lifecycle.
Campaign Lifted Revenue
Campaign lifted revenue is the additional revenue generated by an email campaign beyond what would have occurred without it, measured via a holdout group or statistical lift analysis.