The passive voice is more common in formal written English. It is often used in newspapers, academic and scientific writing, and reports, which attempt to be less personal. Most passive sentences do not have an agent, as the focus of the sentence is not on the doer of the action but on its recipient. As a rule, the agent is only mentioned in the passive sentence if it is important new information which cannot be omitted:
The Lord of the Rings was written by J. R. R. Tolkien.
While Tony was walking home last night, he was mugged by a group of young men, who stole his mobile phone and wallet.
The passive voice is preferred over the active in the following cases:
