The 1940 version of the film, starring Laurence Olivier and Greer Garson, reused costumes from 1939's "Gone With the Wind." Consequently the costumes feature hoop skirts and corsets in the style of the latter film's era, anachronistically setting the film decades later than Austen's book.
The 1980 BBC miniseries also reuses many costumes from other productions, but is more historically accurate than the 1940 film. Rather than using costumes from Civil War period dramas, most of the clothes come from the 1972 series "Emma," also based on a book by Jane Austen.
The costumes in the 1995 BBC miniseries, starring Colin Firth and Jennifer Ehle, are accurate to the setting of 1813, the year of the book's publication. This period is noted for its high waistlines in women's clothing, and knee-breeches with tall boots for men.
The 2005 film also features historically accurate costumes, though intentionally set in an earlier time-period than most adaptations---1790, the year Austen wrote the first draft of "Pride and Prejudice," entitled "First Impressions." The older women wear even earlier fashions, while Caroline Bingly, a character from London, wears newer clothing that didn't become widespread until later in history.