What is it?
Lookback is an advanced setting that is not required. It allows you to define how much time you allow AdRules to consider before making changes.
How does it work?
Allows user to define how many days the algorithm should 'look back' when calculating ad performance to apply rules
Strategy and recommendations
To illustrate how to use this feature, let's use an example. If you set your lookback window to 7 days you may run into the following challenges:
- Ad Sets that are doing very well today are not allowed to take off / spend more money today because the system is looking backwards for 7 days of data and taking a blended average of 7 days of data before making a decision.
- Conversely, if an Ad Set is doing very poorly today, AdRules will not pause the Ad Set because the system is looking backwards for 7 days of data and taking a blended average of 7 days of before making a decision.
As a gross generalization, if you have a conversion rate < 20% you will want a longer lookback window (i.e. > three or four days) and if you have a conversion rate > 20% you can use a shorter lookback window like three days (see above screen shot).
By allowing you to define a time window that matches with your business needs and conversion rates, you get better controls:
- Reliability: Data from past few days is usually a more stable performance indicator than intraday performance or lifetime performance
- Ad burn-out: If an ad set with strong lifetime data starts performing poorly, the system is able to take corrective actions
- Intraday volatility: When an ad set doesn't have enough data/spend on a given day, the system is able to look at a more reliable set of data
For additional clarification on ad set status definitions, please visit our Ad Set Groups - Ad Set Status article.
How do I choose a lookback period?
The lookback period should not be so long that the algorithm wouldn't react to recent performance fluctuations. Also, it should not be so short that there aren't enough conversions for individual ads to make reliable decisions.
Usually, a lookback period of 2 to 3 days is recommended if your conversion rates are > 25% and 4-5 days if your conversion rate is < 25%. For conversion rates < 5%, you may need much longer lookback windows like 7, 14, 21 or even 30 days.
- An account with high conversion rates can afford to have a shorter lookback period
- An account with low conversion rates needs to have a longer lookback period
How does having a shorter or longer lookback period affect performance?
For shorter lookback periods, recent ad performance (current day and past few days) becomes more important when making bidding and budgeting decisions, whereas it becomes less and less important as lookback period becomes longer.
What is the benefit of using day-parted lookback period?
Once there is enough reliable data for current day, it can be useful to give current day performance a higher weightage. This is achieved by reducing the lookback period by 1 day at a pre-defined time every day.