Explain CPA for Meta Ads

Business Context

A mid-market ecommerce advertiser is reviewing performance of its Meta campaign across Facebook Feed, Instagram Reels, and Stories in Ads Manager. The client says, "Our CPA increased last month, but purchases also went up. How should we interpret that, and what should we do next?"

Metric Scenario

In April, the advertiser spent $120,000 and recorded 2,400 purchases attributed in Meta Ads Manager, for a CPA of $50. In May, spend increased to $150,000 and attributed purchases increased to 2,500, for a CPA of $60. CTR fell from 1.8% to 1.5%, landing page view rate fell from 70% to 62%, and purchase conversion rate from landing page view to purchase improved slightly from 3.8% to 4.0%. Reels represented 20% of spend in April and 35% in May. The client wants a clear explanation of CPA that is simple enough for a non-technical marketing lead but still analytically correct.

Requirements

1. Define CPA precisely in the context of Meta Ads Manager and explain what it does and does not measure.
2. Calculate CPA for both months and interpret the change.
3. Decompose the CPA movement into likely drivers using the funnel metrics provided.
4. Explain how you would communicate trade-offs between volume growth and efficiency to the client.
5. Identify what additional cuts of data you would review before recommending budget changes.

Data Available

• meta_ads_delivery: campaign_id, ad_set_id, ad_id, date, spend, impressions, clicks, landing_page_views, placements
• meta_conversions: date, campaign_id, purchases, purchase_value, attribution_setting
• creative_metadata: ad_id, format, objective, audience_type, country
• audience_breakdown: age_bucket, gender, placement, device_os, spend, purchases