Ever wonder why the biggest market for pick-up trucks — that is, the U.S. — has so few trucks available?

Yes, there are the big brands — mostly made by the Big Three. But smaller brands and smaller trucks are surprisingly reticent about cashing in on the most lucrative (highest profit margin per vehicle) segment of the American automobile market.

It all goes back to the so-called "chicken tax," which was signed into law in 1963 by Lyndon Johnson. It was a retaliatory measure directed at France and West Germany, which had imposed tariffs on the importation of American chicken. The measure hit back with tariffs on potato starch, brandy and light trucks, with the object of making all of them about 25 percent more expensive to import and therefore less profitable to sell here.

This explains why, for the most part, they're not sold here. Take, for example, the Ford Ranger, which is made outside the U.S. and is therefore subject to the tariff. So Ford sells the Ranger pretty much everywhere except here.

The tariff mostly affects foreign-brand (as well as foreign-made) medium and compact-sized models like the Toyota HiLux, which is smaller than the Tundra Toyota sells here and also the Mitsubishi Triton, the Mazda B-Series and the new VW Amarok.

Those are just a few of the models most Americans have never heard of, let alone test-driven.

And it's not just that American buyers are denied these choices. The cloistered market is less competitive and less innovative as a result. Compact trucks are big all over the world — Toyota, for instance, has sold more than 16 million HiLuxes. But why should GM, Ford or Chrysler try to develop competing models or sell them here when there's no competitive pressure to offer them?

Some foreign manufacturers have taken the radical step of moving operations here. This circumvents the tariff because the truck is now considered a "domestic" rather than an import — regardless of the brand on the fender.

This is the real reason why Honda built a plant in Alabama to build the Ridgeline — the company's first U.S.-available pick-up. And it's why Toyota built a plant in Texas (truck central) to build the full-size Tundra. Nissan's Titan pick-up is built in Canton, Mississippi - not Hiroshima, Japan. And so on.

In fact, all of the currently available "import" brand pick-ups are actually made in the USA.

This is why there are so few — relatively speaking — "import" brand pick-ups available for sale in the USA.

Currently, there are just two medium-sized ones (the Nissan Frontier and the Toyota Tacoma) and two large (1500 series) models (the Nissan Titan and the Toyota Tundra).

That's it. The smaller outfits can't afford to add $2 billion or $3 billion to their capital costs by building a whole new plant just to sell a new truck, especially when they already have a plant located outside the U.S. As a result, Americans are denied access to models that almost certainly would receive a warm welcome, such as Volkswagen's Amarok.

Because of the chicken tax, American truck buyers get the limited choice of a full-sized truck or a mid-sized truck, for which they will pay more up front and more down the road on gasoline. This is particularly ironic given all the Washington blather about gas-mileage and saving the planet.

The good news is the "chicken tax" may finally be on its way out. Part of the Trans-Pacific Partnership trade deal that's winding its way through Congress would roll back the tariff over a period of years and eventually eliminate it.

TPP itself is a typical product of the Beltway sausage-making process. But it's hard to argue against putting the chicken tax on the chopping block. It will mean more truck options and lower costs for Americans. If only it hadn't taken 50-plus years to do it.

Eric Peters is an automotive journalist and author. His next book - "Doomed" - will be available this winter. Thinking of submitting an op-ed to the Washington Examiner? Be sure to read our guidelines on submissions.