Post #G21-025: Demonstrating the scope of the canning lid shortage via a random sample of Walmarts

Posted on May 22, 2021

I first wrote about the 2021 canning lid shortage in March (Post #G21-003).  The number of hits on that posting continues to ramp up, suggesting that, if anything, the lid shortage may be getting worse.

But how bad is it?  How often are canners across the U.S. going to their local hardware or other stores and finding empty shelves where the lids ought to be?  Am I getting hits from a few scattered localities where lids are unavailable?  Or is this really a nation-wide shortage of lids?

I considered and rejected doing a simple internet poll to gauge how widespread the shortage is.  Internet polls are unreliable in the best of circumstances.  But in this case, it’s a fair bet that almost all the people who found that poll would be people who were searching the internet trying to find canning lids.  The results from a poll like that would be even-more-useless than the average internet poll.

It occurred to me that the Walmarts provide an easy and relatively unbiased way to gauge the true extent of the shortage.  They are the largest U.S. retailer.  They more-or-less blanket the country.  It’s tough to find a town in the contiguous U.S. that isn’t within driving distance of a Walmart.  They all carry canning supplies.  And you can check the stock on-line.

Question:  If you walked into a randomly-selected Walmart in the U.S. today, whats the likelihood of finding canning lids on the shelves?

I decided to estimate that using a random sample of ZIP codes as my starting point.  That’s for convenience, because the Walmart website will find your nearest store by ZIP code.  It’s not an ideal sample because it has a strong rural bias relative to the distribution of the population.  (There are more ZIP codes per person in rural areas than in urban areas, or, restated, rural ZIP codes tend to have fewer people in them.) That said, for a proof-of-concept, and an attempt to see whether or not the lid shortage is nation-wide, this seemed adequate.

I started with a 2014 list of ZIP codes that I had obtained years ago from  I excluded ZIPs that have no physical extent, such as ZIP codes for post office boxes.  I used the Excel RAND() function to assign a random number to each of the roughly 22,000 remaining ZIP codes.  I sorted to find the top 20 based on that random number, then went to the Walmart website to check availability of packages of wide mouth canning lids at the the Walmart nearest to each of those 20 ZIPs.

Answer:  15 percent chance.

That’s a small sample, and it has a rural bias.  But I think this demonstrates that this really is a nation-wide shortage.

But it’s still a “soft shortage” of lids.  In almost all of the ZIP codes I looked at, Walmart would ship up to three packages of lids per order (but no more than three).  The ZIPs where that wasn’t true appeared to be ZIPs where some store in the area had them in stock.  The upshot is that if you are willing to pay the shipping (or can find enough other goods to reach $35 to qualify for free shipping), you actually have access to a modest supply of lids, at a reasonable price, anywhere in the U.S.A.

Finally, here’s the list of 20 ZIPs for which I checked stock at the nearest Walmart.