W3Schools is a website for people with an interest for web technologies. These people are more interested in using alternative browsers than the average user. The average user tends to use Internet Explorer, since it comes preinstalled with Windows. Most do not seek out other browsers.
These facts indicate that the browser figures above are not 100% realistic. Other web sites have statistics showing that Internet Explorer is used by at least 80% of the users.
Anyway, our data, collected from W3Schools' log-files, over a five year period, clearly shows the long and medium-term trends.