Once you start moving [market] lower, then you trigger of all sorts of things. You trigger people who have to sell because they're over-levered. So they sell their winners and their losers. They're just trying to raise cash. So, what you then get is spreading malaise throughout the global markets.

How long can interest rates stay negative? Think about this. Not only are you lending your money to governments, but you're paying them interest for the privilege of doing so.

America's downgrade may serve as a wakeup call for its policymakers. It is an unambiguous and loud signal of the country's eroding economic strength and global standing. It renders urgent the need to regain the initiative through better economic policymaking and more coherent governance.

The one instrument that has relative political autonomy is monetary policy. Central banks do not need to go to Congress to get approval for an interest rate hike.

As a whole, investors should welcome attempts to safeguard the integrity of markets. You need very clear rules applied to markets.

As we spend more, and as companies are pushed to invest, they say, "Hey wait a minute! There's more demand in the system. Let's invest more."

Investors should be cautiously positioned as the global economy and markets face major uncertainties. The downgrade will be a further headwind to growth and job creation in the U.S.