http://www.huffingtonpost.com/eric-roth/the-real-wizards-of-oz-de_b_1166422.html
Visual effects are the true “movie stars” of big studio pictures — they turn today’s movies into box office hits the same way big name actors ensured the success of classic films. In fact, 46 of the 50 top worldwide Box Office films of all time were visual effects-driven. And movies and broadcast programs you wouldn’t think of as visual effects driven routinely utilize “invisible” effects to make changes to hair color, the sky, or to the background of a scene — even creating the entire backlot and sets.