17. The system of claim 10 wherein the search engine is further configured to use comparisons of the predictive outputs of the model with an implicit user feedback model to adjust respective ranking scores of the given search results.
17. The system of claim 10 wherein the search engine is further configured to use comparisons of the predictive outputs of the model with an implicit user feedback model to adjust respective ranking scores of the given search results. 18. The system of claim 17 wherein the implicit user feedback model is a click fraction, and the search engine is configured to use a comparison of the predicted click through rate and the click fraction to adjust the respective ranking scores of the given search results, the comparison including at least one of a ratio of the predicted click through rate and the click fraction or a value difference between the predicted click through rate and the click fraction.