The winner
No prizes for guessing that a certain juvenile conjuror reigns supreme at the North American box office. Harry Potter and the Half-Blood Prince proved it had the chops to extend the franchise's winning ways. And how. Harry and his magical mates delivered an estimated $159.7m (£96.7m) over five days, making it the second biggest five-day entry of the year behind Transformers: Revenge of the Fallen's $201m effort last month. Half-Blood Prince raked in a record $22.2m in its initial midnight screenings last Wednesday and went on to take $58.2m on its first day. For the record, Half-Blood Prince grossed $79.5m from Friday to Sunday.

Stats aside, the point is that the sixth Potter adaptation smeared egg all over the faces of the nay-sayers. Some people said Warner Bros had a dud on its hands after it moved the film's release back from last autumn, when in fact the studio was unflagging in its belief that the exact opposite was true and only wanted to exploit the movie during the lucrative summer months. Others thought Half-Blood Prince held limited appeal because it would be the first in the series to go on release after all the books had been published, which always struck me as a specious argument. It turns out that knowing how the saga ends hasn't kept the crowds away in the slightest. The franchise will soon overtake James Bond to become the biggest in history.

Warner Bros' distribution head has said Half-Blood Prince stands a good shot at becoming the only Harry Potter title since Philosopher's Stone in 2001 to cross $300m in the US. It's already done that internationally, having racked up a record $396.7m in its first five days.

The loser
Vassup Bruno? One week you're being hyped as comedy's equivalent of the new black, destined to join your stablemate Borat in the box-office pantheon, and the next you're, well, so last weekend. Final results come in later today, but based on estimates Bruno dropped off a cataclysmic 73% in its second weekend, adding only $8.4m to its running total of $49.6m. That puts it in the top 30 of biggest drops, an inglorious accolade indeed. By this stage Borat had grossed $67.1m from significantly fewer cinemas. Why is this happening to Bruno? Not a lot of people like him.

The dark horse
Fox Searchlight's comedy 500 Days of Summer entered the charts at No 12 after taking $838,000 for an excellent average gross of $31,037 from 27 sites. That's a strong start for the movie, which premiered at Sundance at the start of the year and frankly didn't endear itself to many festivalgoers. Moon and The Hurt Locker are looking good and are well positioned in the charts to capitalise on strong reviews and a lot of goodwill – Moon sits in 16th place and has taken $2.7m from 252 cinemas after six weekends, while The Hurt Locker shot up four places to No 13 in its fourth weekend and has grossed $2.2m from only 94, ahead of its imminent expansion.

The real story
Box office is slowing down, but only by a fraction. For a second consecutive weekend the combined ticket sales of the top 12 movies trailed the same period last year, according to box-office trackers. This weekend the aggregated $159.1m was 39% behind the corresponding 2008 weekend. To be fair, the weekend of 18-20 July 2008 was a bit out of the ordinary: that's when The Dark Knight launched on an astounding $158.4m.

The future
Harry Potter shouldn't have much trouble taming Disney's guinea pigs-with-gadgets action movie G-Force. There are also wide releases for Warner Bros' horror movie Orphan, which from the marketing campaign at any rate looks like any other bad-seed story, and Sony's romcom The Ugly Truth, with Katherine Heigl from Knocked Up and Britain's very own Gerard Butler.

North American top 10, 17-19 July 2009
1. Harry Potter and the Half-Blood Prince, $79.5m. Total: $159.7m
2. Ice Age: Dawn of the Dinosaurs, $17.7m. Total: $152m
3. Transformers: Revenge of the Fallen, $13.8m. Total: $363.9m
4. Bruno, $8.4m. Total: $49.6m
5. The Hangover, $8.3m. Total: $235.9m
6. The Proposal, $8.3m. Total: $128.1m
7. Public Enemies, $7.6m. Total: $79.5m
8. Up, $3.1m. Total: $279.6m
9. My Sister's Keeper, $2.8m. Total: $41.5m
10. I Love You, Beth Cooper, $2.7m. Total: $10.3m

• Jeremy Kay writes for Screen International in Los Angeles