Predictive Model Performance

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for analyzing outcome estimation models. In one aspect, a method includes providing tracer data to a content performance estimation model. The tracer data specify feature values for a reference content item that is not distributed to users, and for which a reference performance measure is pre-defined. An estimated performance measure that was computed for the reference content item is received from the performance estimation model. An accuracy measure is computed for the content performance estimation model using the estimated performance measure and the reference performance measure. Data are provided that specify the accuracy measure for the content performance estimation model.