On Sept. 15, 2008, Lehman Brothers, a venerable international financial firm, went bankrupt. Its collapse set off a chain of events that triggered a global financial crisis that is estimated to have caused more than $1.6 trillion in losses and cost millions of jobs. A year later, we are still assessing the lessons of the Lehman debacle. Incredibly, one year later, little if anything has been done to prevent another such collapse in the future.

Lehman Brothers was one of the oldest financial firms in the United States. Founded in 1850, during the 1980s it became the fourth-largest investment bank in the U.S. with the highest return on equity in the industry. From 1994 — when it went public — until 2007, the firm increased net revenues over 600 percent from $2.73 billion to $19.2 billion, and the number of employees increased from 8,500 to over 28,000. That history and track record were not enough to stave off disaster last year, when losses from its holdings of subprime mortgage loans forced it to sell assets at fire sale prices and start laying off employees.

Those steps were not enough to restore confidence in the firm. Its stock price plummeted and creditors began calling in loans. Unable to meet those demands, and finding no other party — in particular the U.S. government — willing to lend it a hand, Lehman Brothers filed for bankruptcy Sept. 15, 2008, the largest failure of an investment bank in nearly two decades.

Lehman's collapse triggered a drop in the Dow Jones Industrial Average of just over 500 points, the biggest fall since the terror attacks of Sept. 11, 2001. Investors the world over worried that other financial institutions faced similar problems. A crisis of confidence rolled across global financial markets, and banks and other institutions quit lending money out of fear that it would not be returned. And with that, the greatest economic crisis since the Great Depression truly began.

The U.S. government's failure to bail out Lehman stunned banking officials. France's financial minister called the decision "horrendous" and a "genuine mistake," an opinion that was shared by the head of the European Central Bank. For some observers, U.S. inaction actually caused the debacle, transforming a crisis into a global collapse. U.S. officials insist that they did not have the legal authority to help the company.

With the benefit of hindsight, however, most analysts now believe that it was only a matter of time before something went sour. Too many financial institutions were overexposed, holding long-term paper whose value was evaporating and short-term deposits that they could not pay back in a pinch. If Lehman Brothers had not been the trigger, then another equally vulnerable banking institution would have done the trick.

Those same observers believe that it was the shock of the Lehman Brothers' failure that galvanized the U.S. to take action. That is probably too optimistic an assessment. The U.S. Congress debated the bailout plan for several weeks; it voted down several attempts at a bailout. More disturbing is the continuing failure to take concrete steps to avoid a repetition of the crisis and the return of dubious practices among bankers.

On the anniversary of the Lehman collapse, U.S. President Barack Obama spoke in New York City to strengthen efforts at financial market reform. He wants to shore up regulation of financial institutions, figure out ways to limit the speculation that led to the imbalances in balance sheets, and create a new consumer protection agency that would put an end to the abusive lending practices that created the subprime mess. Unfortunately, Mr. Obama has been distracted by the battle over health care reform, his signature issue.

Meanwhile, old excesses are making a comeback. Bank profits — and associated bonuses — are again in the stratosphere. The Dow has reclaimed a good part of its losses. The financial sector has consolidated, making big banks even bigger and increasing the prospects of catastrophic failure. Brokers have begun repackaging assets, a practice that looks suspiciously like the bundling of subprime mortgages, which started the downslide a year ago.

In fact, national action alone will not solve the problem. One of the most important lessons of the past year is that the global financial system is indeed global. Only coordinated, multilateral action has a chance of success. Thus, financial regulation now tops the Group of 20 agenda and will dominate the upcoming meeting in Pittsburgh scheduled late this week.

A global pay code will provide some satisfaction, especially if it prevents bankers from profiting from their recklessness. But financial safety and security will only result from a regulatory regime that has the power to oversee all financial institutions and ensure that reward is tied to risk-taking. It is the gap between the two, and the near certainty that calamitous decisions will not only go unpunished but will be offset with a bailout, that brought about the harrowing events of the past year. The most important lesson of the past year is that this sad state of affairs must stop.