For most of human history, if you wanted something, you got it from someone nearby. Your food came from local farms. Your clothes came from local weavers. Your tools came from local blacksmiths. Trade happened, sure — the Silk Road moved spices and silk across continents — but it was slow, expensive, and risky. A merchant could spend months on a single journey and still lose everything to weather or bandits. The world was big, and most of it was effectively unreachable. Then three things changed everything: steamships, telegraphs, and later, container shipping. Suddenly the cost of moving stuff — and information about stuff — collapsed. And when moving things gets cheap, the entire logic of who makes what gets rewritten from scratch.

Here's where your earlier lesson on comparative advantage pays off — and where the shirt question from the top finally gets its answer. Remember: countries don't just trade what they have in abundance — they specialize in what they're relatively best at producing, even if another country could technically do it better. Globalization is comparative advantage operating at full speed, across the entire planet, in real time. Bangladesh has low labor costs and a massive textile workforce — comparative advantage in garments. South Korea has deep engineering expertise and capital — comparative advantage in semiconductors. Brazil has land, climate, and scale — comparative advantage in soybeans and beef. When trade barriers fall and shipping gets cheap, every country doubles down on its strengths and imports everything else. The result is a world where almost nothing is made in one place anymore.

And here's where it gets complicated. Globalization creates enormous wealth — the data on this is overwhelming. Global extreme poverty fell from 36% of the world's population in 1990 to under 10% by 2015. Countries that plugged into global trade — South Korea, Taiwan, China, Vietnam — saw living standards explode in a single generation. The gains are real. But those gains aren't distributed evenly, and this is where a lot of political fury comes from. When a factory moves from Ohio to Vietnam, Vietnamese workers get jobs and Ohio workers lose them. Total global welfare goes up. Ohio's welfare goes down. The people who benefit from globalization and the people who pay its costs are often completely different people in completely different places — and the winners rarely compensate the losers. That mismatch is behind a lot of the trade wars, tariff fights, and economic nationalism you've seen in the last decade.