The Complete Guide to Marketing Attribution for Ecommerce

You're running Meta Ads, Google Ads, email marketing, and maybe some influencer campaigns. Each platform says it's driving sales. But the numbers don't add up. Welcome to the attribution problem.

Why Attribution Is Broken

Every platform wants credit for your sales. Meta counts anyone who saw your ad in the last 7 days. Google counts clicks. Klaviyo counts anyone who opened an email before purchasing.

Add them all up and you've sold 3x more than you actually sold. That's because they're all taking credit for the same purchases.

iOS 14 made this worse. Privacy changes mean platforms have less data. They're modeling and estimating more than ever. The numbers in your ad dashboards are increasingly unreliable.

Attribution Models Explained

Last click: All credit goes to the final touchpoint before purchase. Simple but ignores the full journey.

First click: All credit goes to the first touchpoint. Good for understanding acquisition but ignores everything that nurtured the sale.

Linear: Equal credit to all touchpoints. Fair but doesn't account for different impact levels.

Time decay: More credit to touchpoints closer to purchase. Makes intuitive sense but still somewhat arbitrary.

Position-based: 40% to first touch, 40% to last touch, 20% split among the middle. Balances acquisition and conversion.

There's no perfect model. Each has tradeoffs. The key is picking one and being consistent.

The Practical Approach

Here's what actually works for most ecommerce brands:

Step 1: Track everything in one place

Use Google Analytics or a dedicated attribution tool as your source of truth. Don't rely on individual platform dashboards. They're biased toward their own performance.

Set up proper UTM parameters for all campaigns. Every link should be tagged so you can see where traffic actually comes from.

Step 2: Look at blended metrics

Calculate your blended ROAS: Total revenue divided by total ad spend. If you spent $10,000 across all channels and made $30,000, your blended ROAS is 3.0.

This cuts through attribution noise. You know how much you spent and how much you made. Everything else is details.

Calculate your MER (Marketing Efficiency Ratio): Total revenue divided by total marketing spend (including agency fees, creative costs, etc.). This is the truest measure of marketing efficiency.

Step 3: Run incrementality tests

The only way to know if a channel truly works is to turn it off and see what happens. Scary but effective.

Start with smaller channels. Pause for 2 weeks. Did revenue drop by more or less than expected? That tells you the true incremental value.

Do geo tests for bigger channels. Run ads in some regions, not others. Compare performance.

Platform-Specific Notes

Meta Ads

View-through conversions inflate numbers. Someone saw your ad, then searched your brand name on Google, purchased, and Meta takes credit.

Look at 1-day click attribution for the most conservative view. Compare to 7-day click + 1-day view to see the gap.

Google Ads

More accurate for click-based tracking but still overcounts. Brand searches get attributed to campaigns even if people would have searched anyway.

Segment brand vs non-brand. True acquisition comes from non-brand searches and display prospecting.

Email (Klaviyo)

Influenced attribution counts anyone who received an email before purchasing. Accurate attribution requires actual clicks.

Look at direct revenue (clicked email and purchased) vs influenced revenue. Direct is what you can truly credit to email.

Tools for Better Attribution

Triple Whale: Built for Shopify. Good dashboards, reasonable cost, integrates well with ad platforms.

Northbeam: More sophisticated modeling. Better for larger spends. Higher price point.

Google Analytics: Free and surprisingly powerful if set up correctly. Use GA4 with proper ecommerce tracking.

Post-purchase surveys: Ask customers how they heard about you. Simple but effective for understanding the real journey.

The Honest Truth

You'll never have perfect attribution. The customer journey is too complex, privacy changes continue, and platforms have incentives to overclaim.

Focus on:

• Blended metrics that cut through the noise
• Directional data to guide decisions
• Incrementality testing for major channels
• Consistent measurement over time

If your blended ROAS is profitable and trending in the right direction, you're winning. Don't get lost in attribution debates. Focus on growing the business.