It is worthwhile to note that there are other, smaller publishers in the Courseware business. Wiley, MacMillan, and SAGE all have higher education textbook businesses, often with one or more areas of specific focus (for example, Macmillan has an historic focus on the social sciences and humanities, and Wiley has always been very visible in business). OpenStax, a nonprofit open textbook publisher operating out of Rice University, has successfully launched a set of introductory for high enrollment courses. These textbooks are openly licensed, free online, and available in print at a low cost, and are also backed by a marketplace of optional supplemental materials.
Estimating market share among publishers has been difficult. Higher education publishers report their revenues to the AAP (Association of American Publishers), which aggregates and circulates them. The consistency of the reporting has been called into question, however, in part because there is no clarity about whether all of the publishers are consistently reporting their courseware revenues (some may include sales of teaching materials, while others may only report courseware shipments). Additionally, revenues are reported at the time of shipment (minus provisions for estimated returns), so publishers could potentially inflate revenues in any one quarter or year by shipping larger numbers of books during that time (or lowering their estimates for returns). Finally, as publishers scrambling to ink deals with institutions that trade higher sell-through rates in exchange for temporary discounts, revenues may not be the most reliable indicator of market share at this point of transition.