Alexander Payne’s high-concept “Downsizing” has its up and downs. It starts out as a fable about folks who will literally shrink themselves to the size of a doll to pursue a better life. Then it veers off track.

Alexander Payne’s high-concept “Downsizing” has its up and downs. It starts out as a fable about folks who will literally shrink themselves to the size of a doll to pursue a better life. Then it veers off track.

Payne penned the script with longtime writing partner Jim Taylor (“Citizen Ruth,” “Election,” “About Schmidt,” “Sideways”) and they use it admirably to promote big ideas about social justice, the environment and consumerism. Before the movie ventures into unexpected territory, it’s an absurd original with pitch-perfect satire.

It opens in Norway, where scientists have perfected the shrinking process, an effort they hope will solve overpopulation, deemed to be “humanity’s greatest problem.”

But while the science community celebrates the worldwide benefits of downsizing – less consumption, less waste, etc., Americans, naturally, see the tiny life as a way to live like kings because their money goes further in a miniaturized world – $150,000 is worth about $12 million. That’s the motivator for Omaha Steaks occupational therapist Paul Safranek (Matt Damon, displaying that aw-shucks everyman appeal that’s typical of a Payne protagonist ) and wife, Audrey (Kristen Wiig). They decide to abandon their sad-sack middle American existence and shrink to a 5-inch version of themselves to live in pint-sized luxury at Leisureland, a self-sustaining community of the small in New Mexico.

The first hour is full of Payne’s droll wit propping up the lunatic premise. It’s fun and funny, with supporting turns from Wiig, Jason Sudeikis, and Neil Patrick Harris and Laura Dern as Leisureland’s slick salespeople. You wish they’d all stick around longer.

When Paul wakes up from the procedure his life is vastly different. The script then jumps ahead a year. Paul lives tiny but still reels from a big personal crisis. Enter Dusan (Christoph Waltz), the hedonistic neighbor who urges Paul to live a little.

And this is where the movie takes a sharp right. The second hour is so vastly different from the first that it feels like two separate movies. In fact, it feels nothing like a Payne movie. With its sci-fi touches, special effects and international flair, “Downsizing” is a bit of a departure for the Nebraska-bred Payne. What propels the second half is the Oscar-worthy performance from Hong Chau, a Vietnamese dissident who’s shrunk for punishment. Chau, who received supporting actress nominations from both the Golden Globes and Screen Actors Guild, is no small wonder.

For Payne, an Oscar-winning writer for “The Descendants” and “Sideways,” this is his first movie since “Nebraska” four years ago. It’s refreshing to see directors take risks and “Downsizing” certainly doesn’t lack originality. That’s a wave of fresh air in a year where the highest-earning films have been superhero flicks (“Wonder Woman”), sequels (“Star Wars: The Last Jedi) or book adaptations (“It”). However, inventiveness only goes so far. “Downsizing” doesn’t know what it wants to be. And that identity crisis is “permanent and irreversible,” just like the downsizing procedure.

Dana Barbuto may be reached at dbarbuto@ledger.com or follow her on Twitter at @dbarbuto_Ledger.

DOWNSIZING (R for language, nudity, and drug use) Cast: Matt Damon, Kristen Wiig, Christoph Waltz, Hong Chau. Grade: B-