Bond Rating Agencies and Stock Analysts: Who Knows What When?
比较债券评级机构与股票分析师的信息时效性，发现两者存在双向因果关系：债券降级前通常已有盈利下滑，但降级本身也会引发分析师下调盈利预测。
Both bond rating agencies and stock analysts evaluate publicly traded companies and com? municate their opinions to investors. Comparing the timeliness of each, we find that Granger causality flows both ways. While most bond downgrades are preceded by declines in actual and forecast earnings, both actual earnings and forecasts of future earnings tend to fall following downgrades. Although part of this post-downgrade forecast revision can be attributed to negative news regarding actual earnings, most appears to be reaction to the downgrade itself. We find little change in actual earnings following upgrades. Analysts, however, tend to increase their forecasts of future earnings.