1 Introduction
Search engines have become a necessity in our daily life, as the search engines empower us to find our desired information rapidly from the vast volume of web pages. Search engine business has thus become one of the most profitable businesses on Internet. Meanwhile, search engine providers also face fierce market competition [17], [27]. Prior studies show that 70% of users rely on multiple search engines and due to the low switching cost, engine switching happens frequently [44]. Earning loyalty can be critically important for search engine providers. Customer loyalty has long been regarded as a vital source of sustained profits, which enables a company to develop a sustainable advantage over competitors [1]. Retaining merely 5% of customers can improve profits by almost 100% [28]. Therefore, effectively tracking user loyalty and understanding how and why loyalty changes and users leave become particularly indispensable for search engine providers.