Domestic box office saw the biggest year-over-year down slide so far this year, at 45%, but it’s not all due to the East Coast blizzard or Universal’s “Identity Thief,” which overperformed with an estimated $36.6 million.

No, the downturn is attributable mostly to a lack of product, when last year had two $40 million-plus openers, “The Vow” and “Safe House.”

The storm named Nemo did have an impact on the weekend box office, though mostly on Friday, with theater closings spanning the Northeast. And while box office lost an estimated 10% because of the storm, weekend totals, at just north of $100 million, still would have trailed last year by roughly 40%. Last weekend, totals dipped below 2012 by roughly 23%.

Identity Thief,” which cost $35 million to produce, still ranks among the top 10 largest domestic openings for an R-rated comedy.

Internationally, Sony’s “Django Unchained” claimed its fourth straight weekend victory, with $18.7 million, for an overseas cume of $187.1 million. Fox’s “A Good Day to Die Hard” got off to a strong start in seven Asian territories, earning $10.1 million a week before its Stateside debut.

Aside from “Thief,” the only other wide release this weekend was Open Road’s Steven Soderbergh thriller “Side Effects,” which came in line with expectations (for third place) estimating a tad north of $10 million. The $30 million-budgeted pic actually did best in the Northeast, where it earned roughly 18% of its gross.

“Side Effects” lost to Summit’s soph-sesh holdover “Warm Bodies,” down just 43%, for a weekend gross of $11.5 million and a cume of $36.7 million domestically.

A few other stalwart holdovers, like “Argo” and “Wreck-It Ralph,” saw sizeable upticks, growing 23% and 79% in their 18th and 14th frame, respectively. “Argo,” which added 470 locations this weekend, earned $2.5 million, while “Ralph” estimated $1.1 million with just 97 additional engagements.

“Argo” has cumed $123.7 million domestically; “Ralph” reached $184 million.

Paramount’s “Top Gun” 3D re-release debuted with a projected $1.9 million from 300 Imax locations, averaging $6,333 per screen. Gross marks a solid start to the conversion’s exclusive six-day theatrical run.

Meanwhile, local Chinese blockbuster “Lost in Thailand” failed to garner much Stateside support, averaging a paltry $833 from 29 AMC locations, for an estimated three-day take of $29,143.

Nemo steals B.O. heat

While box office in the Northeast suffered on Friday, most designated metropolitan areas on the East Coast rebounded quickly on Saturday. New York, for instance, was up 306% Friday-to-Saturday. The market, which typically ranks first during most weekends came in at No. 4 overall in two days.

Boston and the surrounding areas were hit harder, however. That DMA, which usually comes in at No. 7, fell to No. 93 this weekend.

“When you look at the affected heavyweight markets like New York and Boston, there’s no doubt that ‘Identity Thief’ could have reached $40 million,” said Universal distribution prexy Nikki Rocco. “I think the marketplace was right for a comedy.”

In general, “Identity Thief” overperformed throughout middle America in such markets as Phoenix, Detroit, Houston, Dallas, Cleveland and Kansas City. Rocco attributed the perf to stars Melissa McCarthy and Jason Bateman, with few comedies bowing lately.

“Identity Thief,” which “Horrible Bosses” helmer Seth Gordon directed from a script by Craig Mazin, opened higher than previous PG-13-rated comedies around this time, including last year’s “Just Go With It.” Pic also debuted to more than “Bridesmaids,” at $26 million, though it won’t have the same legs as “Bridesmaids,” which played through the summer.

Jason Cassidy, marketing prexy for Open Road, said “Side Effects” is positioned well in the marketplace as an adult-skewing thriller that should trump waning year-end awards fare.

“There’s definitely an audience for this type of movie,” Cassidy said. “It’s a fun ride.”

“Side Effects,” which stars Channing Tatum, Rooney Mara, Jude Law and Catherine Zeta-Jones, skewed 63% female, with an overwhelming 85% of the opening crowd over 25.

The film increased 47% Saturday-over-Friday, which was mostly due to East Coast theaters re-opening, but also a sign of healthy word-of-mouth. Like “Identity Thief,” the Open Road pic scored a B CinemaScore.

‘Django’ chain unbroken

Holdover markets again led the charge for “Django Unchained,” including Germany, which contributed $3.9 million, down 41%, for a cume of $35.6 million, followed by France, with $3.3 million (off just 33%) and $27.3 million locally.

The winning streak likely won’t hold for “Django,” as “A Good Day to Die Hard” expands throughout much of the world this week.