Its first weekend out of the gate, The Help lost at the box office to Rise of the Planet of the Apes. But since, the Civil-Rights-era drama about the African-American servants of white women has been the top film for three straight weekends. It brought in $19 million over Labor Day weekend, making it the first film since Inception to hold the top spot for so long, and winning coveted labels like "surprise summer hit" and "unlikely juggernaut." Why has The Help been such a success? Here, five theories:

1. It's a good movie
The Help is a "worthy movie" that is "certainly deserving" of its success, says Scott Gwin at CinemaBlend. Too often "little movies with great stories" don't get enough credit and fare poorly at the box office. Not this time.

2. It's been blessed with middling competition
The Help has benefitted from a lack of other good movies over the last month, says Gwin. Apollo 18 and Shark Night 3D aren't exactly Titanic. Yeah, says Grady Smith in Entertainment Weekly. Some of The Help's success must be attributed to "audience's general disinterest in the majority of August's poorly-reviewed offerings."

3. It's been propelled by good buzz
Credit "the strong word-of-mouth The Help has been enjoying," says Smith, noting the film's A+ grade on CinemaScore. Indeed, people are talking, says Amy Kaufman in the Los Angeles Times. And that invaluable word-of-mouth is pushing The Help to box-office gold.

4. It's appealing to an older audience
The under-25 set has "recently seemed indifferent to summer releases," allowing films targeting more mature audiences, like The Help and The Debt (which came in at #2 this weekend), to rule the box office, says Andrew Stewart in Variety. The Labor Day holiday isn't typically a box office bonanza, but these "adult-skewing pics kept weekend totals from falling too far behind."

5. It's not a 3D superhero movie
This summer, "studios bet heavily on 3-D and superhero movies" and lost, say Rob Golum and David McLaughlin at Bloomberg. The surprise hits of the season are The Help and Bridesmaids, both female-centric films with a mere two dimensions. Their success "underscores Hollywood’s challenge in keeping up with changes in audiences' tastes." Audiences have come to realize that "3D has been a gimmick in the past," says Box Office Mojo's Brandon Gray, "and there's no evidence to suggest it's much more than a gimmick now."