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A trader watches prices at his post at the New York Stock Exchange at the opening bell August 8, 2011. - 

Today the Marketplace Index debuts; but hardly as expected. When planning this show about the markets and what they say about the economy, we failed to make contingency plans for a hurricane threatening Wall Street. And while Irene left New York relatively unscathed, there were worries that the markets may not open for business today.

But those worries were overplayed; Wall Street isn't really Wall Street anymore. The New York Stock Exchange has one-third the floor traders it had a decade ago. No, Wall Street today is banks of computers across the world.

Today we went to the hallowed floor of the NYSE to talk to Teddy Weisberg of Seaport Capital. He's been a member of the NYSE for more than four decades. He explains the changes he's seen over the years, all based on improvements in technology.

Weisberg says that some of these technology improvements have increased general volatility - the high speed trading that has cut the time it takes to buy and sell a stock down to milliseconds.

However Weisberg also stated that, despite all the improvements in technology, the markets still run on the one thing that computers can't replace: human emotion.

Follow David Brancaccio at @DavidBrancaccio