It’s hard to find controlled experiments in finance. But they exist. East and West Germany, North and South Korea, Chile and Venezuela. In crossing a border, you can immediately see the difference in economic output and financial well-being from one country to the next, based on variations in tax and regulatory policy. The same goes for within the United States …

The stock market is at a record high. Investors are chasing a handful of hot stocks. Geopolitical tensions threaten to upend the rally. I’m referring, of course, to 1972. The S&P 500 Index closed at a record high of 119.12 on December 11. It was the height of the Nifty Fifty (not to be confused with the Nifty 50 Index …

The real loser in Catalonia’s referendum was, of course, Spanish Prime Minister Mariano Rajoy. He needs to make sure that his country’s bond market doesn’t follow suit. The regional election he demanded resulted in the three separatist parties winning 70 out of the 135 seats. But the pro-independence parties did not win an overall majority of votes, and forming a …