The world became simultaneously bigger and smaller last week. Smaller, because in homes and offices all over the globe we were able to see immediately the full horror of what was happening in New York as events unfolded. Bigger because, with flights grounded and no way of getting to the US, the Atlantic had never seemed wider.

When news stories break, those in financial services are nearly always the first to know. The scrolling headlines of Reuters and Bloomberg screens mean that every story, no matter how big or small, appears on a dealer's desk. Last week, some of my ex-colleagues learned of the most horrific story ever because their feeds from New York went blank or because telephone lines went down.

It's not surprising, therefore, that many dealers are still in a state of shock and, despite a willingness to "get things back to normal", there are some events that cannot be dealt with by the usual dealer's method of making a black joke or a shrug of the shoulders.

There are many dealers who, notwithstanding whatever the market throws at them in the next few weeks, will feel buying and selling bonds and equities will forever take a lower place in their priorities. And still, in some way, it seems disrespectful towards those who have suffered to talk calmly about the likely progress of the economy or where the markets go from here. To say that not to do so would mean that the terrorists "have won" doesn't make it easier.

Although the news reports continually stressed the fact that south Manhattan is the heart of New York's financial district, there are many other businesses in that area. Whatever about the giants of the global economy being able to regroup (and they will), there are many smaller businesses that will never recover.

The US economy was already faltering before September 11th. Consumer confidence was at an eight-and-a-half-year low and jobless claims had risen.

These statistics were beginning to generate pessimistic analysis as to the ability of the US to avoid recession.

The accepted definition of a recession is two consecutive quarters of contraction. This may now happen. But many of us thought it was likely to happen anyway. And although a fall into recession might be exacerbated by the terrorist attack, and although this was unparalleled in its ferocity and tragedy, most individual events usually have only a temporary effect on major economies.

Nevertheless, short-term consumer confidence will definitely have taken another severe blow. Nobody is thinking of buying new clothes, redecorating the house or making new investments when they are numbed with shock and grief.

As far as those who are in industry are concerned, it's difficult to get your mind back to the job when images of people jumping to their deaths are etched forever in your thoughts. Those who were in south Manhattan and escaped will surely be damaged emotionally for some time. So one of the biggest changes as far as the average American is concerned will be psychological - whether or not they have the interest or enthusiasm to invest. Initially they won't. Eventually they will.

Clearly, there are industries that will be badly affected. The market has made its call on the airline industry, which was already under pressure due to the slowing economy. The additional costs associated with increased security will put question marks over the viability of many more airlines (even if some of the more ludicrous security measures are simply knee-jerk reactions).

Estimated claims of between $30 billion (€32.7 billion) and $100 billion are being suggested for insurance companies, a sector that wouldn't otherwise have been as dramatically affected by a slowdown.

Many US brokerage companies will struggle. Transatlantic tourism will suffer. TV networks, which gave comprehensive coverage to the explosions and aftermath, may have gained millions of viewers but they have lost millions of dollars in foregone TV advertising. And, of course, retail industries will have lost sales, not just in the past number of days but in the future too.

However, there are companies that will make money in the months to come, not least of which are data-protection companies. Most banks and financial institutions keep back-ups of their data in locations well away from their actual business place. Many companies have simulation days, where main systems are taken off-line so they can check how well the back-up works. Many others, especially those in perceived high-profile locations, may now choose to have off-site backup.

Defence companies are clearly going to do well. And, for the hard-pressed technology sector, there will be demand for product to replace some of what was destroyed.

Business leaders need to be able to motivate workers, who will clearly be shocked for a long time. If any event will ever divide the wheat from the chaff, it is this. Executives who rose to the top courtesy of spin, luck and share options, may well find themselves ill-equipped to deal with a new reality. Those with character and determination will drive their companies forward with the support of their employees.

Companies that have benefited from years of using sweatshop labour in far-flung corners of the globe may well find that access to their merchandise is harder, and increased transport and security costs will eat into their profit margins. Companies that have invested at home will reap the rewards of a patriotic US public.

Like many people, I have spent a lot of time in reflection. I hope I'm never called on to be as brave as many New Yorkers have had to be. I have been impressed by the courage and integrity of the financial community in its darkest hour.

I know that there will always be causes worth dying for. But, as the full horror of this tragedy and so many other terrorist actions show, there will never be a cause worth killing for.