What effect dose illiteracy has on a person and country?

Living now in the 21st century, children as young as the age of 3 are taught the basics of phonetics and language. If you're illiterate in our world, you basically have no chance of survival. Warning signs, important labels, street signs, and everything around our world evolves around Literacy. America is one of the highest-literacy rated countries in the world, and being able to read and write with proper grammar, is essential.