In the five years since Lehman Brothers collapsed, setting off the financial crisis and Great Recession, there has been plenty of time for I-told-you-sos, finger pointing and blame dodging.

But if one steps back to look at the forest instead of the trees, a few questions arise: Have any big lessons been learned? Have regulators, lawmakers and executives figured out how to prevent this kind of mess in the future?

The verdict is mixed, according to a number of economists. The banking system, for example, has been strengthened with tougher capital and liquidity requirements. But the underlying cause of the recent financial crisis, like many before it, remains a threat: the ever-present potential for a real estate bubble.

“Financial crises are … an inherent part of having a developed financial system, and it’s hard to believe that we can completely avoid them,” says Wharton finance professor Itay Goldstein, adding: “At the end of the day, the financial system is fragile.”

Mark Zandi, chief economist at Moody’s Analytics, believes the government’s tougher capital requirements – essentially, requiring more cash on hand for emergencies — have indeed made banks safer, while other new rules help ensure that loans are made only to borrowers likely to repay. But, he adds: “I don’t think we’re there yet. I think regulators still need to address too-big-to-fail issues.”

The too-big-to-fail dilemma, where the government feels it must bail out a financial institution so it won’t drag others down, is more challenging today because the top firms are bigger than they were five years ago. “If anything, the turkey is even fatter than before, in the form of the large banks,” says Kent Smetters, professor of business economics and public policy at Wharton. He feels little has been done to prevent another crisis. “Large banks are impossible to seriously risk-manage.”

“Financial crises are … an inherent part of having a developed financial system, and it’s hard to believe that we can completely avoid them.”

Also unimpressed by recent remedies is Wharton finance professor Krista Schwarz. “Some measures to prevent future crises have been implemented as part of Dodd-Frank,” she says, referring to the massive 2010 reform act. “But the overall response seems weak.”

The crisis, she says, revealed – once again – “the enormous conflicts of interest within the financial system,” where executives can get rich taking risks with other people’s money, even if that means endangering their own firms. It also, she says, underscored the need for “hard caps” on leverage, or borrowing by financial institutions to place risky bets, and it showed that regulators should act to head off asset bubbles before they get too large. But Schwarz is not convinced that regulators, lawmakers and other players have taken these lessons to heart.

Real Estate: An Incomplete Market

One particular asset bubble – housing – was at the core of the recent crisis. But look into the heart of just about any financial crisis and the same thing is apparent — a burst real estate bubble, says Wharton real estate professor Susan M. Wachter. She ticks off a long list, including the U.S. savings and loan crisis of the 1980s and 1990s, the “lost decades” crisis in Japan, the “Asian contagion” of the late 1990s and a Mexican crisis around the same time.

“There have been many others,” she says. “It’s not because people in real estate are particularly dumb; it’s because real estate is an incomplete market…. You can’t short-sale the real estate that you own or the securities that back it up.”

An investor who believes stocks will lose value can, of course, sell his or her shares. But in addition to avoiding a loss, he can make money on the price decline by selling borrowed shares in hopes of replacing them with ones bought for less. In addition to these short sales, investors can profit on declines with “put” options and other derivatives based on individual stocks, market sectors or the market as a whole.

These opportunities allow people with negative views on the stock market to play a strong role in setting prices, often putting a break on excessive enthusiasm. But because there is no comparable system in real estate – you can’t short-sale your home or buy a put option on it – pessimists can only retreat to the sidelines, leaving optimists to continue bidding prices higher, according to Wachter.

There have been some attempts in recent years to create securities that would permit profiting on a real estate decline, but none has so far been able to establish a sizeable, liquid market, she says, although she is hopeful that some current efforts will bear fruit.

Profit incentives, of course, also play a role in real estate bubbles. Lenders want to lend, and as long as real estate prices are rising, it looks like homes provide good collateral. But because the pessimists have little role, the optimists can continue driving prices up and arguing that property values are high enough to justify big loans, Wachter notes. In the recent crisis, lenders also engaged in a “race to the bottom,” making ever-riskier loans in their fight for market share. When real estate values started to fall, the house of cards collapsed.

Federal regulators and lenders have toughened lending standards in the wake of the crisis, banning products like “liar loans” that did not require applicants to show proof of income. But bubbles, Wachter observes, do not require bizarre loans – they have occurred in countries that did not have the kinds of toxic mortgage products that triggered the U.S. crisis.

“I still think that, unfortunately, there is just not wide recognition that real estate asset markets are fundamentally different from other asset markets.”

The underlying forces that cause real estate bubbles are still with us, she concludes, and because real estate is a huge market, it can bring down the entire economy when things go bad. “I still think that, unfortunately, there is not wide recognition that real estate asset markets are fundamentally different from other asset markets.”

Classic Bank Run

Though the recent crisis involved a lot of newfangled products like credit default swaps and synthetic collateralized debt obligations, it was, at its heart, not very different from a classic bank run, Goldstein notes. Instead of long lines of depositors trying to withdraw their savings, this one was manifest in withdrawals from mutual funds, credit freezes and tumbling derivatives values – all arising from a lack of trust, just like the bank runs of the old days. Players suddenly worried they wouldn’t get paid money they were owed, so they pulled back.

While the U.S. has had its share of financial and economic troubles since the Depression, a catastrophe on the scale of the Depression-era bank runs had long seemed to be a thing of the past due to safeguards like federal deposit insurance, which guarantees bank savings, Goldstein says. The potential for a bank collapse, therefore, received little attention in recent decades at the same time that investment banks, as opposed to the old-fashioned commercial banks, became larger players.

“A lot of the finance profession basically looked at how to make money in the stock market, at what explains patterns of risk and returns and things like that,” Goldstein says. “To a large extent, there was not enough attention paid to the topics of financial fragility and financial crisis. But things were building up under the surface.” Gradually, he adds, regulations were relaxed, and the banks were allowed to take on more and more risk, the key to making outsized profits.

The constant pressure to take more risk continues to build so long as nothing goes wrong. The process is prodded along by moral hazard – a term that refers to increased risk-taking — spurred by the belief that someone, such as the government, is standing by with a bailout. Worried about moral hazard, regulators allowed Lehman Brothers to go under five years ago, but were then horrified by the crisis that followed and scrambled for remedies.

Today, critics say efforts like the Troubled Asset Relief Program, government spending to spur economic growth and Federal Reserve efforts to keep interest rates low were ill conceived, slowing the recovery. Defenders say such measures — even though they were flawed because of the rush to apply them — prevented a second Great Depression.

“We know what the government did, and we know what happened, but we don’t know what would have happened if the government had done something different,” Goldstein says. “By and large, I think the response was adequate.”

But as the big banks grow bigger, it’s unclear just what will happen if one bank gets into enough trouble to go under. New regulations require each bank to have a “living will” detailing steps for shutting down in a crisis, but regulators are still likely to fear the consequences of letting a big financial institution collapse, Goldstein notes. That can encourage the banks to take on more risk. Indeed, there have been numerous cases of big banks taking unwise risks in the years since the crisis. Just this week, the “London Whale” trading scandal led to $920 million in fines for JPMorgan Chase. As part of the settlement, the firm admitted wrongdoing, citing “poor internal controls,” according to The Wall Street Journal.

“My guess is that the decision to let Lehman Brothers fail probably would not have been taken if people knew what the consequences would be,” Goldstein says. “I think one thing we perhaps learned is that there can be very, very severe implications for letting such a huge financial institution fail, because [these institutions] are so interconnected.”