Sometimes an essay begins with a "grabber," such as a challenging claim, or surprising story to catch a reader's attention.
The introduction should be designed to attract the reader's attention and give him/her an idea of the essay's focus.
Attention-grabbers should go at the very beginning of an essay to hook your reader.
As a general rule, numbers and statistics can be very powerful rhetorical tools.
Because quantifying phenomena is such a challenge, using a statistic, fact, or number immediately draws your readers' attention and impresses upon them your mastery of the topic you're treating.