Another complication is release in multiple formats for which different ticket prices are charged. One notable example of this phenomenon is "Avatar", which was also released in 3D and IMAX: almost two-thirds of tickets for that film were for 3D showings with an average price of $10, and about one-sixth were for IMAX showings with an average price over $14.50, compared to a 2010 average price of $7.61 for 2D films. Social and economic factors such as population change and the growth of international markets also impact on the number of people purchasing theater tickets, along with audience demographics where some films sell a much higher proportion of discounted children's tickets, or perform better in big cities where tickets cost more.