Russian troops pour over a border. An autocratic Russian leader blames the United States and unspecified “radicals and nationalists” for meddling. A puppet leader pledges fealty to Moscow.

It’s no wonder the crisis in Ukraine this week drew comparisons to Hungary in 1956 and Czechoslovakia in 1968 or that a chorus of pundits proclaimed the re-emergence of the Cold War.

But there’s at least one major difference between then and now: Moscow has a stock market.

Under the autocratic grip of President Vladimir Putin, Russia may be a democracy in name only, but the gyrations of the Moscow stock exchange provided a minute-by-minute referendum on his military and diplomatic actions. On Monday, the Russian stock market index, the RTSI, fell more than 12 percent, in what a Russian official called panic selling. The plunge wiped out nearly $60 billion in asset value — more than the exorbitant cost of the Sochi Olympics. The ruble plunged on currency markets, forcing the Russian central bank to raise interest rates by one and a half percentage points to defend the currency....