If there’s a sudden drop or increase in global pings or tag fires for a conversion action that your campaign is using for Autobidding, this can result in a drop in serving and spending as Google Ads optimizes towards your set conversion action.
If you’re looking at conversion-related metrics like cost/conversion over recent date ranges, be sure to consider conversion lag (also known as "conversion delay").
If you’re comparing performance to a previous period, your most recent performance might not look as strong because some of the people who clicked your ad haven’t converted yet as conversions can be reported up to 90 days after the click. Since you're missing these conversions that may be reported at a later date, but your spend is fully reported, it may appear that you have fewer conversions, a higher cost per conversion.
What you can do
Use the conversion lag report to understand conversion delay information on key metrics, such as cost-per-acquisition (CPA) or return-on-ad-spend (ROAS). These are used to predict how actual CPA or ROAS values may change once adjusted for conversion lag.Your Google Ads account
Need something else?
Check other common reasons why your campaign performance is fluctuating.