GEOFF BENNETT: Egg prices have soared to new records over the last couple of months.

The wholesale price for a dozen white eggs climbed to over $8 in February.

Since then, that price has come down, but prices consumers pay at the grocery store are still high.

Our economics correspondent, Paul Solman, takes a look at what's been going on.

PAUL SOLMAN: Egg prices once again no joke, the price for a dozen eggs, up 60 percent in a year.

But why?

Typically, some 300 million American hens lay some 90 billion American eggs every year.

Seems like enough to go around.

So why would prices suddenly take wing?

The answer appears to be the oldest cliche in economics, supply and demand.

So first, supply.

It's been drastically reduced by the flu.

Here's agricultural economist Jada Thompson.

JADA THOMPSON, University of Arkansas: Highly pathogenic avian influenza, or we kind of call it bird flu, is a disease of poultry.

It leads to at least 75 percent mortality.

And that's in chickens.

And this one is more like 90 to 94 percent mortality.

And so you have this huge mortality either dying from the disease or being depopulated in order to keep the viral loads down.

And so as of November of last year to February of this year, I think we're down 50 million egg-laying birds.

PAUL SOLMAN: But wait, avian flu also hit back in 2015.

That outbreak was pretty much over in months.

Emily Metz speaks for the egg industry.

EMILY METZ, CEO, American Egg Board: This virus is clearly evolving.

And our entire supply chain has been impacted, including our young birds, which has made recovery so much slower for this industry.

JADA THOMPSON: We're in unprecedented number of birds out of the system, and that's coming with unprecedented prices.

PAUL SOLMAN: So the supply story is simple.

But it's supply and demand.

EMILY METZ: We have had 23 consecutive months of year-over-year record demand.

PAUL SOLMAN: But here's a question, doesn't demand go down when prices go up?

Well, not if the demand for eggs or anything else is pretty constant and largely unresponsive to price hikes.

JADA THOMPSON: We demand eggs.

Think about all those egg processors that are making breads.

I still buy my bread.

They still have to make bread.

In order to make that bread, they need eggs.

In order to buy those eggs, there's a low supply, so they're going to keep bidding until they get those eggs.

PAUL SOLMAN: The bidding happens on an electronic auction-style market, which helps set the daily wholesale egg price.

More bidders willing to pay more for diminished supply means the price goes up.

And consumer behavior is driving up demand as well because of anxiety buying.

Egg broker Brian Moscogiuri: BRIAN MOSCOGIURI, Eggs Unlimited: Now we have increased demand from the consumers that are buying more eggs than they have ever purchased before.

Some of my friends and my family have sent me pictures where they're typically buying a dozen a week.

They have eight to 10 dozen in their refrigerators because they're seeing the news about what's going on with egg prices and potential scarcity of eggs and stores running out of eggs.

PAUL SOLMAN: Happens to be true of both me and producer Diane Lincoln Estes.

We'd been stocking up before even being assigned this story.

Here's my fridge.

May not look like that many, but three to five more eggs than usual.

Multiply that by America's almost 130 million households and you would have demand for over 600 million more eggs.

EMILY METZ: And I think that's probably happening in a lot of households.

Egg buying has become a paranoia.

PAUL SOLMAN: OK, low supply, high demand, and thus higher prices.

But about 90 percent of wholesale eggs are sold based on long-term contracts between buyers and sellers.

Doesn't that stabilize prices?

BRIAN MOSCOGIURI: It's really the 10 percent of eggs that are negotiated that ultimately set the price, because that's where true value in all commodities is discovered.

It's that day-to-day negotiation to really identify what the value of the eggs are in the open market.

That's where commodity markets are priced and discovered.

And that's not just in eggs.

That could be in oil and gas and different types of commodities as well.

PAUL SOLMAN: Moreover, many of the long-term contracts are based on what short-term buyers have to pay on the daily spot market.

BRIAN MOSCOGIURI: The market is adjusting based on the spot value of eggs, and the contracts are tied to that market, which ultimately will go up or down depending on what the actual market is doing on a day-to-day basis.

PAUL SOLMAN: But here's another question.

Why are egg prices all over the place at grocery stores?

Our producer wanted to know.

WOMAN: When I went shopping for eggs, like, the first place had no eggs whatsoever.

The second place, eggs were anywhere from $8 over $13.

And then I finally ended up at Aldi, where they had a dozen eggs for only $5.79, but they limited two egg cartons per person.

BRIAN MOSCOGIURI: It really depends on the contracts the buyers and sellers have and also the strategy of the retailer and how they want to position eggs as potentially a tool to get people coming into the store.

Eggs are sometimes used as a loss leader, meaning that they will keep egg prices artificially low in order to drive consumers into the store so that they buy other higher-margin items.

When you found the cheapest egg as you shopped around to three or four different stores, did you just buy eggs?

Did you buy more eggs?

Like, what was your shopping experience like?

WOMAN: I never shop at Aldi, but I went and I got my two cartons of eggs and then I looked around and I got other stuff.

And I have been going back ever since.

PAUL SOLMAN: Now, to be fair, skeptics think something else is scrambling the cost of eggs, price fixing.

Cal-Maine, the largest producer and distributor of fresh shell eggs in the U.S., reported an 82 percent jump in revenue in its most recent earnings report.

And the jury did find that large producers were guilty of price fixing back in 2011, but there could be a justification for higher profits right now.

JADA THOMPSON: Cal-Maine or any other company that is able to sell eggs during periods of high price are going to basically win out.

So they get additional prices because they have the only supply that exists.

PAUL SOLMAN: The Department of Justice is now investigating, however.

The industry's response?

EMILY METZ: I can't speak to why the Justice Department is doing what they're doing, but I can speak to the facts, and the facts are very simple.

The price of eggs are set on the commodity market.

PAUL SOLMAN: OK, last question.

What next?

BRIAN MOSCOGIURI: Luckily, right now, it looks like potentially it's slowing, but now we're moving into this spring migratory period, where the wild birds fly across the country, potentially bringing additional risk, as we go into now another demand period, which is the Easter and Passover holiday period, which are typically and seasonally the second highest market levels of the year if you look at the long-term market dynamics.

PAUL SOLMAN: In other words, at the grocery store, you might plan to continue spending eggs-tra.

Sorry.

For the "PBS News Hour," Paul Solman.