By Michelle Fluerry
Business presenter, BBC News, New York
The current credit crisis has led to comparisons with the Great Depression, which for many of us born after the 1930s might not mean a lot.
For Irving Kahn it was the start of his career. He worked on Wall Street at the time of the stock market crash in 1929.
But as he recalls, he was one of the luckier ones.
"I got my pay cut to 60 dollars a week. And I remember my rich employer saying to me 'Why are you smiling?'. And I said 'I thought you were going to fire me'."
At the age of 103, Mr Kahn may be the oldest working financial analyst on Wall Street.
He is chairman of Kahn Brothers, a New York investment firm, and still goes to the office every day searching for undervalued stocks.
So what does he make of recent events?
Mr Kahn warns against drawing close parallels between what the US went through then and the present financial problems.
The nature of the trouble in the credit markets is, as he sees it, far more concentrated: "It's a very narrow crisis because it involves people who borrowed too much money," he says.
This crisis has been unfolding in slow motion over a long period, after Wall Street bet - mostly with borrowed money - that the riskiest mortgages in the country could be turned into sound investments.
But it is not just the result of bad bets on mortgages. Investment banks took on too much risk and now a correction is taking place that has brought down three of the biggest firms on Wall Street.
Among the best known is Lehman Brothers, which filed for bankruptcy protection in September.
The flashing lights at the Times Square building that was once its headquarters are now covered with the logo of British bank Barclays, which bought up a large part of Lehman.
The past few months has also seen Merrill Lynch being snapped up by Bank of America and Bear Stearns being acquired by JP Morgan.
If you visit downtown New York you may come across the sculpture of the charging bull.
The bull market is over
Located near Wall Street, it is one of New York's most photographed artworks.
This symbol of financial optimism has taken a beating and not just from the winter weather.
The last two independent investment banks, Goldman Sachs and Morgan Stanley, have changed their status to that of banks.
Under the rules that govern bank holding companies, they have to raise more capital and they face tougher oversight.
For them, it means the end to a good chunk of their profits.
So with the industry's business model in tatters, is this the death of Wall Street?
Banks act as financial intermediaries in economies. That role still needs to be filled, which is why Roy Smith believes predictions of its demise are unwarranted.
A professor of finance at New York University's Stern School of Business and a former senior international partner at Goldman Sachs, he thinks such pessimism is not justified.
"It's not the death of Wall Street. Wall Street will continue to provide capital market access services in a very robust way in the future," he says.
Part of the reason is that the expertise is there, but that does not mean that there will not be changes.
He thinks there will be a re-examination of the current rules that govern the industry and that could have a profound impact.
"Regulation is going to shape the largest players more so then the rest," he says.
"But by shaping the largest players it may also shape the smaller players because it means the larger players will do fewer things than they were doing, and maybe some of those things will be food for the smaller players."
With the industry restructuring he thinks there may be opportunities for boutique investment banks.
Whatever happens next, in the form that it's existed for decades, Wall Street is gone, and with taxpayers' money now involved, the institutions that survive will do so, for now, under the supervision of the government.
As for Irving Kahn, he has always stuck to the principles of value investing and, whether it is the current financial crisis or another, he continues to do so.