Economist Ed Yardeni is a constant traveller, relentlessly crisscrossing the globe and talking to investors.
It's a two-way flow of information. The former Wall Street economist, who now runs his own consulting business, offers his views on everything from the direction of corporate profits, economic fundamentals, geopolitics and even the latest movies.
And his customers - including asset managers, mutual funds, trust companies, hedge funds, banks and large corporations - share their thoughts about what's going on in their world.
There are a few other things you should know about Mr. Yardeni, who plied his trade at Deutsche Bank, Prudential Securities and E.F. Hutton before striking out on his own. He's not fond of Democrats or Washington, he loves movies and he's a confirmed optimist.
But these days, Mr. Yardeni acknowledges the W-word is high on everyone's mind - worry.
" 'So what is everyone else worrying about?' This is more or less the most frequent question I've been asked in recent visits," he says.
"There's a lot to worry about. However, some of the greatest bull markets in stocks occur when the Wall of Worry seems insurmountable."
Mr. Yardeni is also fond of lists. He recently put together a top 10 list of investor worries, which we've paraphrased and amplified here as a handy guide to why the stock market rally has stalled in recent weeks:
1 Sovereign debt Some analysts worry Greece could be to the sovereign debt market what subprime mortgages were to housing, spreading a new bout of financial contagion, affecting heavily indebted countries everywhere.
2 Washington gridlock Forget about Congress and the Obama administration tackling any of the country's big problems, including this year's record $1.6-trillion (U.S.) deficit.
3 Bloated state and local budgets States are generally barred by law from running deficits. So they must slash expenses or raise taxes to get back on track, causing a drag on the economic recovery. State shortfalls could sap nearly $194-billion from the U.S. economy this year and another $180-million in 2011.
4 Commercial real estate Half of the roughly $1.4-trillion worth of commercial loans coming due over the next four years are already "under water" and could trigger bank losses reaching as much as $300-billion a year, according to a recent congressional oversight panel report released yesterday.
5 Exit strategies The U.S. Federal Reserve and other central banks are carefully laying the groundwork to retreat from all the easy-money policies they put in place to counter the effects of the credit crisis. Fed chief Ben Bernanke is probably singing that old Clash song Should I Stay or Should I Go. Exiting too early could push the economy back into recession, while hanging in too long could trigger inflation.
6 Inflation Some economists worry that inflation is inevitable with all that monetary stimulus sloshing through the system.
7 China So far, Chinese authorities seem to have engineered a soft landing of their economy. But with China now such a force in the world, a setback there could quickly ripple through the global economy.
8 Jobs The recession blew a gaping hole in the U.S. labour market. Just to get back to pre-recession employment levels, the country must create more than eight million new jobs. And that could take years, keeping a lid on consumer optimism and spending.
9 A double-dip in housing Mr. Yardeni says housing remains the "weakest link" in the U.S. economy in spite of historic intervention by the government. The concern now is what happens when the Fed stops buying all those mortgages, interest rates rise and mortgage lenders Fannie Mae and Freddie Mac stop backing every loan in sight.
10 Iran goes nuclear Any hint of real trouble in Iran could destabilize the Middle East, sending oil prices soaring.
Think of all this as a series of worst-case scenarios. Not all of them will come to pass. Indeed, many fears may prove exaggerated.
But it's a good guide to what the traders who move financial markets are fretting about.