Adding to a good’s price does not make its price decline.

It’s worth repeating that a couple of times, because it seems to be getting lost in the discussion about tariffs – in particular, in the discussion about tariffs levied on US commodities. Grains prices have been plummeting, as the chart below showing front corn and soybean prices (source: Bloomberg) illustrates.

There are many reasons that grains prices may be declining, but if “tariffs have been levied on US production” is one of them then there is some really weird economics happening. Corn and soybeans are commodities. Specifically, this means that they are essentially fungible – corn from site “A” is essentially the same as corn from site “B.” So what does this mean for the results of a tariff?

If China stops buying soybeans from the US altogether, it means that unless they’re going to stop eating soybeans they will buy soybeans from Brazil. But if Brazil sells all of their soybeans to China, it means that Germany can no longer soybeans from Brazil. So where does Germany buy its soybeans from? Well, it seems that the US has beans that are not spoken for in this scenario…in other words, when we are talking about commodities a tariff mostly just reorganizes the list of who is buying from whom. If soybean prices are falling because China isn’t buying our soybeans, it means a great deal for Russia or Germany or whoever else is going to buy beans from us instead of from China’s new supplier. More than that, if global soybeans prices are falling because of tariffs then it means that everyone is getting cheaper soybeans because China is changing who they’re buying from. If that’s the case, then we really need to slap tariffs on everything and watch prices decline!

Let’s go back to elementary microeconomics. Adding a tariff is reflected in our product market supply and demand curves as a shift in the supply curve to the left: the quantity that producers are willing to supply at any price declines, because the price to the producer declines. Put a different way, the market price required to induce any particular quantity supplied rises by the amount of the tariff. Now, whether that causes market prices to rise a lot or a little, or quantity supplied to fall by a lot or a little, depends on the elasticities of supply and demand. If demand if fairly inelastic (which seems reasonable – you may be able to substitute for “beans” but it’s hard to substitute for “grains”), then you will see more of a price response than a quantity response, at least in the short run where the supply of beans is fairly inelastic. But that price response is up, not down.

By the way, this gets a little hard to illustrate with supply and demand curves, because with a tariff what you have are now two separate markets and separate prices for the same good. This is what confuses some people – if China is no longer buying from the US, doesn’t that mean that demand for US beans has declined, and therefore prices should decline? The crucial point is that we are talking here about commodity goods, and supplies are fairly interchangeable. If we are talking about Harley Davidson motorcycles, the answer is different because if Europe stops buying Harleys, they have to buy a different product altogether. In that case, the global price of “motorcycles” might be relatively unaffected, but the price of Harleys will rise (and the output decline) relative to other motorcycles. So, a tariff on Harley-Davidson motorcycles definitely hurts the US, but a tariff on soybeans – or even “US soybeans” since that is not a universal distinction – should have virtually no effect on US producers. And certainly, no effect on the global price of soybeans.

There are other reasons that grains prices may be declining. Since Brazil is a major producer of beans, the sharp decline in the Brazilian Real has pushed the US dollar price of beans lower (see chart, source Bloomberg). In the chart below, the currency is shown in Reals per dollar, and inverted. This is a much more important factor explaining the decline in grains prices, as well as one that could easily get worse before it gets better.

I think the discussion of the effects of tariffs has gotten a bit polluted since the decline in grains seems to coincide with the announcement of tariffs from China. I think the price decline here has fed that story, but it’s bad economics. Piecemeal tariffs on commodity products are not likely to appreciably change the supply and demand outcome, although it will result in rearranging the sources of product for different countries. Tariffs on non-commodity product, especially branded products with few close substitutes, can have much larger effects – although we ought to remember that from the consumer’s perspective (and in the measurement of consumer inflation), tariffs never lower prices faced by consumers although they can lower prices received by producers. This is why tariffs are bad – they cause higher prices and lower output, and the best case is no real change.