Soft Frequency Capping for Improved Ad Click Prediction in Yahoo Gemini Native
Michal Aharon, Yohay Kaplan, Rina Levy, Oren Somekh, Ayelet Blanc, Neetai Eshel, Avi Shahar, Assaf Singer, Alex Zlotnik · 2019
Yahoo's native advertising (also known as Gemini native) serves billions of ad impressions daily, reaching a yearly run-rate of many hundred of millions USD. Driving the Gemini native models that are used to predict both click probability (pCTR) and conversion probability (pCONV) is øffset\ -- a feature enhanced collaborative-filtering (CF) based event prediction algorithm. øffset is a one-pass algorithm that updates its model for every new batch of logged data using a stochastic gradient descent (SGD) based approach. Since øffset represents its users by their features (i.e., user-less model) due to sparsity issues, rule based hard frequency capping (HFC) is used to control the number of times a certain user views a certain ad. Moreover, related statistics reveal that user ad fatigue results in a dramatic drop in click through rate (CTR). Therefore, to improve click prediction accuracy, we propose a soft frequency capping (SFC) approach, where the frequency feature is incorporated into the øffset model as a user-ad feature and its weight vector is learned via logistic regression as part of øffset training. Online evaluation of the soft frequency capping algorithm via bucket testing showed a significant $7.3$% revenue lift. Since then, the frequency feature enhanced model has been pushed to production serving all traffic, and is generating a hefty revenue lift for Yahoo Gemini native. We also report related statistics that reveal, among other things, that while users' gender does not affect ad fatigue, the latter seems to increase with users' age.