I definitely think that literacy is an important part of a country's growth. If most of the citizens are not able to read or write, then there is no way a country can run and govern in the most efficient way possible. I think that it is important that such a parameter is regarded.
I think a country's literacy rate is a good statistic to see how well developed the educational system is in the nation and in general the better a country's educational system is the more advanced a country is in general in economic and military ways, so overall literacy is one of the key parameters to look at to determine a country's growth.
In order for a country to grow, it's citizens need to strive to educate themselves and literacy is vital tool in that process. Literacy gives people the power to make necessary choices that can effect their employment, health, government and their families. Reading helps people form new ideas and empowers them to participate in a country's growth.
No, I would not rate literacy as a key parameter in determining a country's growth, because there are so many things that are so much more important. Private property rights is one of the most important things. Solid law enforcement that protects each person from the other is also more important than literacy.