How to Build a Multi-Channel Attribution Model from Scratch

In the modern Australian digital landscape, a customer rarely buys from you after seeing just one ad. They might find you on Google, follow you on Instagram, and then finally convert after receiving an email—multi-channel attribution is the process of assigning credit to each of these touchpoints so you know exactly which marketing efforts are actually driving revenue.

Without a proper attribution model, you risk switching off a 'low-performing' channel that was actually introducing all your high-value customers to your brand. This guide will help you move beyond simple 'Last Click' reporting to a sophisticated view of your customer journey.

Prerequisites: What You Will Need

Before we dive into the build, ensure you have the following assets ready:

• Google Analytics 4 (GA4) installed: This is the foundation for most modern attribution tracking.
• Google Tag Manager (GTM): Essential for tracking specific conversion events.
• A list of your marketing channels: (e.g., Meta Ads, Google Search, Email, Organic Social).
• Historical conversion data: At least 30 days of data is recommended to see patterns.
• Your ABN and Business Details: To ensure your ad accounts are properly verified and linked.

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Step 1: Define Your Conversion Goals

Before you can attribute value, you must define what a 'win' looks like. For most Brisbane businesses, this is either a lead form submission, a phone call, or an e-commerce sale.

Step 2: Implement Robust UTM Tracking

Attribution is only as good as your data. If you don't tag your links, everything looks like 'Direct' or 'Unassigned' traffic.

Use a consistent UTM naming convention for every link you post outside your website.

• Source: (e.g., facebook, newsletter, google)
• Medium: (e.g., cpc, social, email)
• Campaign: (e.g., summer_sale_2024)

Step 3: Link Your Paid Accounts

To see how your paid spend influences the journey, you must link your platforms.

• Go to GA4 Admin > Product Links.
• Link Google Ads, Search Console, and Merchant Centre.
• For Meta (Facebook/Instagram), ensure you have the Meta Pixel and Conversions API (CAPI) installed via GTM.

Step 4: Choose Your Base Attribution Logic

While we are building a custom view, you need to understand the 'Big Three' models:

• First Click: Gives 100% credit to the first way a user found you (Great for brand awareness).
• Last Click: Gives 100% credit to the final touchpoint (The default, but often misleading).
• Data-Driven (Recommended): Uses Google’s AI to distribute credit based on how much each touchpoint actually contributed to the conversion.

Step 5: Map the Customer Journey Length

Navigate to Advertising > Attribution > Path exploration in GA4. Look at the 'Days to conversion' and 'Touchpoints to conversion'.

Step 6: Configure the Reporting Attribution Model

In GA4, go to Admin > Data Settings > Attribution Settings.

• Set the Reporting attribution model to 'Data-driven'.
• Set the Key event lookback window to 90 days for acquisition events. This ensures that if someone saw an ad in January but bought in March, the ad still gets some credit.

Step 7: Create a 'Position-Based' Spreadsheet Calculation

Since automated tools can sometimes be 'black boxes,' savvy marketers often build a manual model to verify data. Create a sheet with these columns:

• First Interaction (40% credit)
• Middle Interactions (20% credit shared)
• Last Interaction (40% credit)

This 'U-Shaped' model is widely considered the fairest for Australian SMEs as it rewards both the discovery and the closing of the sale.

Step 8: Audit for 'Dark Social' and Direct Traffic

Often, a large chunk of your conversions will be 'Direct'. This usually means the attribution chain broke (e.g., someone clicked a link in a PDF or a private WhatsApp message).

Step 9: Analyse the 'Assisted Conversions' Report

This is the most important step for multi-channel success. In GA4, go to Advertising > Attribution > Conversion paths.

Step 10: Set Up Cross-Domain Tracking

If your checkout process happens on a different domain (e.g., an external booking engine like MindBody or a Shopify subdomain), you must enable cross-domain tracking in GA4 Admin > Data Streams. Without this, the 'chain' of attribution breaks the moment they leave your main site.

Step 11: Create a Custom Looker Studio Dashboard

To make this data readable for your team, export your GA4 data into Google Looker Studio.

• Create a table showing 'Source/Medium'.
• Add two metrics: 'Last Click Conversions' and 'Data-Driven Conversions'.
• The difference between these two columns will show you which channels are your 'unsung heroes'.

Step 12: Review and Refine Monthly

Attribution isn't 'set and forget'. Australian consumer behaviour shifts seasonally. Review your model every month. If you notice a channel has a high 'Assisted Conversion' value but high cost, consider if you can move those users to an email list earlier in the journey to save on ad spend.

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Common Mistakes to Avoid

• Ignoring the 'Lookback Window': If your window is too short (e.g., 7 days), you will lose credit for any long-term research your customers are doing.
• Over-crediting Direct Traffic: Always assume 'Direct' is actually the result of a previous touchpoint you failed to track correctly.
• Double Counting: If you look at Meta Ads Manager and Google Ads separately, they will both claim credit for the same sale. Always use a neutral third-party tool like GA4 as your 'source of truth'.

Troubleshooting

• Problem: My conversion numbers in Google Ads don't match GA4.

• Problem: All my traffic shows as 'Unassigned'.

• Problem: I can't see any path data.

Next Steps

Now that you have a multi-channel model, you can begin 'Budget Optimisation'—shifting funds from overpriced last-click channels into the high-value 'assisters' that start the customer journey.

If you find the technical setup of GTM and GA4 overwhelming, our Brisbane-based team can help audit your tracking. Contact Local Marketing Group today to ensure your data is working as hard as you are.