Great chart from McKinsey. Analysts’ EPS forecasts over time with realized EPS over time.

Exceptions to the long pattern of excessively optimistic forecasts are rare, as a progression of consensus earnings estimates for the S&P 500 shows (Exhibit 1). Only in years such as 2003 to 2006, when strong economic growth generated actual earnings that caught up with earlier predictions, do forecasts actually hit the mark. This pattern confirms our earlier findings that analysts typically lag behind events in revising their forecasts to reflect new economic conditions. When economic growth accelerates, the size of the forecast error declines; when economic growth slows, it increases.3 So as economic growth cycles up and down, the actual earnings S&P 500 companies report occasionally coincide with the analysts’ forecasts, as they did, for example, in 1988, from 1994 to 1997, and from 2003 to 2006.

Would recommend reading the article, very good.

From McKinsey Quarterly April 2010: Equity Analysts still too bullish (source)