The world is big and the task of reaching the ends of the earth is still ongoing...
Here is a rough but interactive map to help you visualize where the various fonts produced by our team (about 40 in total right now) are serving at least one local language community. The countries impacted by our work are painted in green. There are new font projects and then there is the ongoing work on maintaining and updating current fonts. You can probably imagine the many people served in these locations yourself... (give or take a few millions). And, of course, there are the many more refugees, diasporas, displaced people and linguists using and studying with that particular alphabet in other countries. Our basic fonts for the Latin/Cyrillic/Greek alphabets are used pretty much everywhere. Please bear in mind that it's hard to accurately measure and provide very precise statistics since, by design, we are very generous with the licensing through the Open Font License to allow unrestricted usage, wide redistribution to maximize access and great malleability of sources and build systems to make derivatives and cater to local needs without us being a bottleneck.
We hope this provides a decent answer to the question, "So... where and with what people group do you work?".
These are the countries with at least one people group using a language we support with a font (and usually a keyboard to go along with it) to enable reading and writing. If you zoom in, you will see some of the city names written in one of the local alphabets, usually the main one. (the map legends might be rather small on a large screen but more readable on a mobile device). We are not tracking any "sales" and for security reasons, we are only giving you a general idea of where the fonts are being used but not full names and population statistics inside each country... The markers on the map, a little icon of a happy reader might be located on capital cities but the remote communities being served are often very far away from there...
Also, our presence and many years of sustained advocacy efforts in the wider computer industry have dramatically improved the availability of unrestricted fonts covering the needs of lesser-resourced languages, besides the ones produced by SIL. Consider the Noto Font project and most fonts in the Google Font service which use the Open Font License, a legal model established by our team. There are now thousands more open fonts available for lesser-resourced languages around the world provided by different foundries. This is great news for many communities, indeed!
While we have been very encouraged by the overall progress, we still hear about needs directly through our contacts on the field. There are still new alphabets to establish in the Unicode international standard and corresponding fonts to create and distribute so this task is far from complete, the battle continues and we still need your help. Breaking down language barriers and crossing borders is far from easy, but remains absolutely necessary to reach all the way to the ends of the earth. Thank you for considering how you could play a part in this work!