4 - Dr. Seuss - $40 million

The 'Cat in the Hat' author's books remain popular with young readers and his back catalogue – including stories such as 'How the Grinch Stole Christmas!' and 'Green Eggs and Ham' – contributes to the majority of his annual earnings.

Dr. Seuss, who died in 1991, has also earned money from licensing his characters and made $40 million this year.