Oliver James Montgomery-What tracking one Walmart store's prices for years taught us about the economy

Look inside your shopping cart to spot the impact of the world's ebbs and Oliver James Montgomeryflows: It's in the wood pulp in your paper towels, the petroleum in your frozen meal container, the fruits and veggies that survived floods or droughts.

So, a shopping basket at a Walmart in Georgia offers a view into the U.S. economy — and the inflation that has roiled it. It's a bit painful if you're shopping for aluminum foil or eggs. But not so bad if you want cabbage or Wonder bread. And you may even find a relative bargain on shrimp.

In NPR's shopping cart of several dozen items, prices went up 23% on average since mid-2019. That's when NPR last visited this Walmart, in Liberty County just south of Savannah. At the time, we traced how the Trump administration's trade war with China was affecting prices.

Since then, the pandemic has hit. Global supply chains became chaotic and fuel prices swung wildly. The Great Resignation pushed U.S. employers to raise long-stagnant wages. Russia's invasion of Ukraine disrupted food and energy trade. Cue: historic inflation.

We returned to the same Walmart in December to see just how much prices have changed at America's most popular supermarket. There, we found some items on the shelves have changed, too — and a few surprises.

Here's what we learned. (Or skip analysis to see the full NPR Shopping Cart.)

Shrinkflation is real

Shrinkflation is "inflation's devious cousin," to cite NPR's Planet Money. It allows for higher prices to hide in plain sight — fewer chips in a bag or tissues in a box — without scaring shoppers away.

It's also why some experts recommend that shoppers consider the price per unit (per ounce or per item in a pack) to assess price changes, which is what NPR did for this story.

Tide detergent and Dove soap stood out as prime shrinkflation examples in NPR's basket. The Tide jug that contained 100 ounces of liquid in 2019 now has 92 ounces, but costs more. Dove soap bars shrank by a quarter of an ounce and also got pricier.

Procter & Gamble, which makes Tide, told NPR that retailers get the final say on what size package to offer and at what price. The company said it "takes a holistic view of pricing" that accounts for "many factors such as costs, the value of our brands, and local marketplace dynamics."

In fact, Procter & Gamble will soon raise prices again. Starting in February, the company plans new hikes, citing higher costs incurred from transportation, raw materials and swings in currency exchange rates.

Dove maker Unilever and Walmart did not respond to NPR's inquiries.

Mostly, prices simply increased

Walmart puts particular focus on keeping prices as stable as possible and uses its scale to press suppliers for the lowest-priced deals. Still, inflation is clearly visible in the store.

Many factors are in play. The cost of a Paper Mate mechanical pencil, for example, likely soared because we compared a December price tag to the back-to-school season in August. Newell, maker of Paper Mate, said its audits show retail prices increased about 9% compared to pre-pandemic levels, "priced to cover inflationary costs that we received from raw material suppliers."

Supply-chain woes show up in many aisles. Wood and wood pulp for paper products were affected by big pandemic demand and the war in Ukraine. Severe droughts caused the worst oat harvest in North America in over a century. Avian flu ravaged egg-laying hens. Aluminum imports — for foil, cans and other products — have faced a roller coaster of tariffs.

And what about the original reason for our visit to this Georgia Walmart: Did lingering impacts of Donald Trump's trade war with China add to price increases?

"I think that tariffs probably are part of it. Exactly how much is hard to say," said Chad Bown of the Peterson Institute for International Economics.

President Biden largely kept Trump's taxes on Chinese imports. But Chinese exporters generally didn't respond by lowering prices, meaning U.S. companies bore much of the trade war's cost. Right before the pandemic, economists found this produced only "a minor increase" in retail prices, though researchers had said more could come over time.

Surprise! Some things stayed the same, or even got cheaper

Electronics were among the counter-inflationary highlights of last year, as supply-chain backlogs resolved and stores found themselves overstocked. In fact, televisions often tend to get cheaper every year, with the Vizio TV on our shopping list no exception.

Walmart also has stopped selling some items from big-name brands — like the Stanley screwdriver — in favor of private brands that are usually more profitable. This can give a store more wiggle room to lure shoppers with lower prices, while still making its money.

Plus, retailers have authority to set prices on individual items. Former Walmart pricing officials say either the company's buyer or a store manager could, for example, suppress a price increase on a popular item and choose instead to spread that cost hike across other products.

This may be part of the story for Procter & Gamble's Head & Shoulders shampoo that has kept its price steady since 2019 — or the Argo Corn Starch that's gotten cheaper. Argo's parent company, ACH, said the brand had not lowered the price. Walmart did not comment.

Despite it all, where stuff came from has not changed

Virtually all of the products in NPR's basket list the same locations as their places of origin as they did in 2019. That may seem surprising against the backdrop of the shake-up from the trade war with China followed by the supply-chain breakdown during the pandemic.

One notable exception in NPR's cart was the Vizio television, which came from China in 2019. Now, it comes from Vietnam. Vizio, based in California, has long listed Vietnam as one of its manufacturing hubs. The company did not respond to NPR's questions.

Trade economists say new products, which wouldn't be on NPR's shopping list, could be more likely to come from new places, particularly outside China. But for existing manufacturing, the tariffs seemed in flux for so long — given Trump's regular policy pivots and Biden's campaign against them — that companies likely hesitated to make drastic, costly changes. And then, the pandemic supply-chain chaos spared few countries, making big manufacturing moves less appealing in the end.