How many languages in the world are unwritten?

The exact number of unwritten languages is hard to determine. Ethnologue (25th edition) has data to indicate that of the currently listed 7,168 living languages, 4,178 have a developed writing system. We don't always know, however, if the existing writing systems are widely used. That is, while an alphabet may exist there may not be very many people who are literate and actually using the alphabet. The remaining 2,990 are likely unwritten.