Last-click attribution: This assigns all the credit for the conversion to the last-clicked ad and the corresponding keyword.2. First-click attribution: This assigns all the credit for the conversion to the first-clicked ad and corresponding keyword.3. Linear attribution: This allocates the credit for the conversion equally across all ad interactions on the conversion path.4. Time decay: This attribution model assigns greater levels of credit to ad interactions that happened at points that are nearer to the conversion. Credit is distributed through the use of a 7-day half-life. Essentially, an ad interaction that happens 8 days before a conversion gets half as much credit as an ad interaction 1 day before a conversion.5. Position-based: This attribution model assigns 40% of credit to both the first and last ad interactions and corresponding keywords, with the remaining 20% being spread out across the other ad interactions on the path.6. Data-driven: In this attribution model, the distribution of credit for a conversion based on your past data for this conversion action. The biggest difference between the data-driven attribution model and other attribution models is that the data-driven model makes use of your account's data for the purpose of calculating the actual contribution of each interaction across the conversion path.