When Rousseau wrote his social theory, concepts of liberty and freedom were not new ideas. Hints of social contract reasoning are found in earlier works, most notably in Book 2 of Plato's dialog The Republic, as well as, in Socrates.
The total spending per iTunes account is $43 per year across all media, says Dediu. At 575 million iTunes accounts, that works out to $24.7 billion of consumer spending at iTunes per year. The average iTunes account's annual spending on software has followed music's trend, falling to $9 from $42 in 2008. However, average annual spending on apps has gone in the opposite direction, rising to $16 this year from $7 in 2008.
The short answer is $1 at a time. In some countries, the app costs about $1 to download; in others, the first year is free but, each subsequent year costs $1. With over 700 million active users and about 1 million new users per day, yearly revenue can be estimated at $700 million per year.