An interesting tidbit in the latest Status of Global Mission - the annual growth rate of adults (those over 15) is 1.57%, vs. the annual population growth rate of 1.19%. The differences in these two speeds indicates the aging of the world: it is driven by the low birth rates and slowing birth rates in much of the world.
But far more interesting: literate adults is growing from 76.7% to 83.4%. Do the math, and this equates to growth from 3.2 billion literates to 4.5 billion literates. That's an annual growth rate of 2.1% - almost double the annual population growth rate (not quite double the adult AGR). The world is becoming more literate.
Subtracting the literate adults from the total adult population, and we find that the number of illiterate adults dropped from 0.99 billion in 2000 to 0.911 billion today, declining at -0.56% per annum.
The bottom line is this: the world is becoming increasingly more literate - but there are still nearly a billion illiterate adults. Most of these will be among the less-reached peoples. (And these numbers do not include those under 15, many of whom are illiterate among the unreached, nor the "functionally illiterate," nor those who are only literate in a language lacking a Bible translation.)
Orality strategies will be key for at least the rest of this century!