Attribution in ecommerce remains fragmented across platforms: Google Ads reports ROAS, Meta tracks conversion value, email platforms report revenue per send, and affiliate services track commissions separately (Practical Ecommerce). To address this, the Marketing Efficiency Ratio (MER) offers a unified view by comparing total revenue to total marketing spend (Practical Ecommerce).
The calculation is simple: MER = Total Revenue ÷ Total Marketing Spend (Practical Ecommerce). For example, an ecommerce company generating $500,000 in sales with $100,000 in total marketing spend (including advertising, agency fees, and affiliate commissions) would have an MER of 5, meaning $5 in revenue for every $1 spent on marketing (Practical Ecommerce). Unlike ROAS, which measures individual campaigns or channels, MER assesses whether the entire marketing investment produces adequate revenue (Practical Ecommerce).
For commerce practitioners, MER avoids attribution arguments by taking a blended view across all touchpoints and channels, helping teams set spending guardrails based on profitability thresholds (Practical Ecommerce). However, accuracy depends on including all costs—advertising, agency fees, affiliate commissions, influencer costs, software, creative production, and marketing labor—and maintaining consistency month to month (Practical Ecommerce).