In Part 6 of this series I wrote that “18, ultimately 26, countries with different economies, cultures, habits and disciplines are taking a lot for granted when they agree to operate under one common currency.”

Imagine running the central bank whose mission it is to “safeguard the value” of a currency used by 18, ultimately 26, countries with different economies, cultures, habits and disciplines. That’s the European Central Bank (ECB).

Think about it; you have Germany manufacturing goods galore and exporting them to its fellow Euro-using (Eurozone) members without the old constraints that came with fluctuating currencies: In the old days, when the deutsche mark rose in value against, say, the Greek drachma, the price of a Mercedes would rise, in drachma terms, and, therefore, Greeks would buy fewer German cars—or anything else Greeks buy from Germans. Conversely, when the mark declined in value German exports (cheaper in drachma terms) would rise. If you care a lot about exports (not saying you should), you like it when your currency is weak.

In comes the Euro, one currency for all, and German exporters, whose home economy is way stronger than, say, Greece’s, has no worries that such disparity—that would otherwise have driven the mark higher against the drachma—would negatively impact their ability to export to eager Greeks. And, my oh my, export, and lend—out the wazoo—to eager Greeks they did.

Ah, but when those eager Greeks run their debt to the stratosphere and—in an economic downturn (guess they forgot the economy is cyclical)—can’t pay their bills, in a Euro world they can’t simply print up a bunch of drachma and inflate away their troubles. And those balance-sheet-healthy Germans—so proud of their financial prowess—are none too eager to sign onto the printing up of a bunch of the common currency to bailout their profligate customers. Hence, the European (as opposed to the Greek [Italian, Portuguese, Spanish, French]) debt crisis…

Fast forward to today—this Thursday actually—having stepped away from the abyss, ECB President Mario Draghi, who has vowed to do whatever it takes (backstop everybody, somehow), is about to announce yet greater measures to keep the Eurozone economies afloat. I suspect I’ll be reporting on what that means at the end of the week.

So why do we care? As I wrote in Part 6: The Eurozone member countries make up more than half of the EU, the largest trading bloc on the planet. Thus, Eurozone monetary policy is very important to the rest of the planet.

So, from a global economic standpoint, the ECB is huge. From a stock market standpoint (think international trade and, thus, corporate earnings)—as I pointed out in Part 6—it’s of course huge as well.

From another angle: Should Draghi announce some dramatic monetary easing policy this Thursday—such as implementing American-style quantitative easing (that’d be tough given their dynamics), or making member banks pay the ECB interest on excess reserves (easier)—and if that announcement succeeds in forcing Eurozone interest rates lower, U.S. debt looks yet more attractive, which could result in yet lower U.S. interest rates (although I could argue that if the “market” thinks that whatever Draghi conjures up will actually help the economy, the threat of faster growth could actually force interest rates higher). Now go back to Part 2 where I talk about how interest rates impact stock prices.

There are other angles to consider—such as the impact Eurozone monetary policy has on foreign currency exchange rates—but I think the above scratches the surface enough for you to understand why, as adviser to many of my readers, the ECB is something I pay very close attention to…