What Fraction of Images on the Web Contain Text?

Web search engines index text represented in symbolic form. However, it is well known that a fraction of the text on the web is present in the form of images, and the textual content of these images is not indexed by the search engines. This fact immediately raises a few questions: i) What fraction of the images on the web contain text? ii) What fraction of the text content of these images does not appear in the web page in symbolic form? Answers to these questions will give the web users an idea about the amount of information being missed by the search engines, and, justify whether or not Optical Character Recognition should be a standard part of search engine indexing. To answer these questions we statistically sample the images referenced in the web pages retrieved by a search engine for specific queries and then find the fraction of sampled images that contain text.