First click, last click, linear - attribution models change how you credit your marketing channels.
Attribution is the process of determining which marketing touchpoints deserve credit for a conversion. A customer might see your Google Ad, visit your website, leave, see your retargeting ad on Facebook, come back, and then call you. Which channel gets the credit for that lead? The answer depends on your attribution model.
Last-click attribution (the default in most platforms) gives 100% of the credit to the final touchpoint before conversion. In our example, the phone call from the website gets all the credit, and the Google Ad and Facebook retargeting get nothing. This model undervalues the channels that introduce customers to your brand.
First-click attribution gives all credit to the first touchpoint - in this case, the Google Ad. This model is useful for understanding which channels are best at generating awareness but ignores the role of nurturing channels like retargeting in converting that awareness into action.
For most service businesses, a data-driven or linear model gives the most balanced view. Linear attribution splits credit equally across all touchpoints. Data-driven (available in Google Ads with enough conversion volume) uses machine learning to assign credit based on which touchpoints actually influence conversions. The key takeaway is: understand that no single channel works in isolation, and avoid making budget decisions based solely on last-click data.