Why Ignore Macroeconomic Factors?
From Warren Buffett's 1994 Shareholder letter:
 
"We will continue to ignore political and economic forecasts, which are an expensive distraction for many investors and businessmen. Thirty years ago, no one could have foreseen the huge expansion of the Vietnam War, wage and price controls, two oil shocks, the resignation of a president, the dissolution of the Soviet Union, a one-day drop in the Dow of 508 points, or treasury bill yields fluctuating between 2.8% and 17.4%."
 
"But, surprise - none of these blockbuster events made the slightest dent in Ben Graham's investment principles. Nor did they render unsound the negotiated purchases of fine businesses at sensible prices. Imagine the cost to us, then, if we had let a fear of unknowns cause us to defer or alter the deployment of capital. Indeed, we have usually made our best purchases when apprehensions about some macro event were at a peak. Fear is the foe of the faddist, but the friend of the fundamentalist."
 
"A different set of major shocks is sure to occur in the next 30 years. We will neither try to predict these nor to profit from them. If we can identify businesses similar to those we have purchased in the past, external surprises will have little effect on our long-term results."
 
"We try to price, rather than time, purchases. In our view, it is folly to forego buying shares in an outstanding business whose long-term future is predictable, because of short-term worries about an economy or a stock market that we know to be unpredictable. Why scrap an informed decision because of an uninformed guess?"