بازده سهام، شگفتی درآمد کل و امور مالی رفتاری

We study the stock market's reaction to aggregate earnings news. Prior research shows that, for individual firms, stock prices react positively to earnings news but require several quarters to fully reflect the information in earnings. We find a substantially different pattern in aggregate data. First, returns are unrelated to past earnings, suggesting that prices neither underreact nor overreact to aggregate earnings news. Second, aggregate returns correlate negatively with concurrent earnings; over the last 30 years, for example, stock prices increased 5.7% in quarters with negative earnings growth and only 2.1% otherwise. This finding suggests that earnings and discount rates move together over time and provides new evidence that discount-rate shocks explain a significant fraction of aggregate stock returns.

This article studies the stock market's reaction to aggregate earnings news. Prior research shows that stock prices for individual firms react positively to earnings news but require several quarters to fully reflect the information in earnings, an empirical finding known as “post-earnings announcement drift” (see Kothari, 2001, for a literature review). Our goal is to test whether post-earnings announcement drift shows up in aggregate data and, more broadly, to understand the connection between market returns and aggregate earnings surprises. The motivation for our study is twofold. First, we provide a simple out-of-sample test of recent behavioral theories, including Bernard and Thomas (1990), Barberis et al. (BSV) (1998), and Daniel et al. (DHS) (1998). Those studies all cite post-earnings announcement drift as a prime example of the type of irrational price behavior predicted by their models. Our reading of the theories suggests that, although they are motivated by firm-level evidence, the biases they describe should also affect aggregate returns. While we do not view our paper as a strict test of the models, our analysis is in the spirit of asking whether the theories can “explain the big picture” (Fama, 1998, p. 291). More generally, establishing whether the same behavioral biases affect firm-level and aggregate returns should help theorists refine models of price formation. Second, we study the market's reaction to aggregate earnings news to better understand the connections among earnings, stock prices, and discount rates. A large empirical literature tests whether stock prices move in response to cash-flow news or discount-rate news, but the importance of each remains poorly understood (see, e.g., Campbell and Shiller, 1988b; Fama and French, 1989; Fama, 1990; Campbell, 1991; Cochrane, 1992; Vuolteenaho, 2002; Hecht and Vuolteenaho, 2003; Lettau and Ludvigson, 2004). Our tests provide direct evidence on the correlation between earnings growth and movements in discount rates. Further, we argue that the market's reaction to aggregate earnings news provides interesting indirect evidence. Our initial tests mirror studies of post-earnings announcement drift in firm returns. Bernard and Thomas (1990) show that, at the firm level, price drift matches the autocorrelation structure of quarterly earnings: positive for three quarters then negative in the fourth. They conclude that investors do not understand the time-series properties of earnings (see also Barberis et al., 1998). Our first key result is that aggregate earnings are more persistent than firm earnings, yet there is no evidence of post-announcement drift in aggregate returns. Aggregate earnings growth is quite volatile and, while positively autocorrelated, appears to contain a large unpredictable component. From 1970 to 2000, the growth rate of seasonally differenced quarterly earnings (dE) has a standard deviation of 17.8%, about half of which can be explained by a simple time-series model of earnings growth (as measured by the regression R2). Earnings surprises seem to be large, so our tests should have reasonable power to detect post-earnings announcement drift. Second, and perhaps more surprising, we find that aggregate returns and contemporaneous earnings growth are negatively correlated. For our main Compustat sample from 1970 to 2000, stock returns are 5.7% in quarters with negative earnings growth and only 2.1% otherwise (significantly different with a t-statistic of 2.0). In regressions, concurrent earnings explain roughly 5–10% of the variation in quarterly returns and 10–20% of the variation in annual returns, with t-statistics between −2.4 and −3.7 depending on how earnings are measured. We find similar results using earnings on the Standard and Poor's Composite Index (the S&P 500 and its predecessors) going back to the 1930s. These results provide strong, albeit indirect, evidence that earnings and discount rates move together. Mechanically, returns must be explained either by cash-flow news (with a positive sign) or expected-return news (with a negative sign; see Campbell, 1991). Earnings surprises are positively related to cash flows, so the market reacts negatively to earnings news only if good earnings are associated with higher discount rates. In fact, we find that earnings growth is strongly correlated with several discount-rate proxies, including changes in T-bill rates (+), changes in the slope of the term structure (-), and changes in the yield spread between low- and high-grade corporate bonds (-). But only the correlation with T-bill rates has the right sign and, together, the proxies only partially explain why prices react negatively to earnings news. The evidence suggests that discount-rate shocks that are not captured by our proxies explain a significant fraction of stock returns (see also Campbell and Shiller, 1988b; Fama, 1990; Campbell, 1991). For the horizons we study, discount-rate news actually swamps the cash-flow news in aggregate earnings. The negative reaction to good earnings is especially surprising because theoretical models often predict that discount rates drop, not increase, when the economy does well (examples include the habit-based model of Campbell and Cochrane, 1999, and the heterogeneous-investor model of Chan and Kogan, 2002). Our results complement Lettau and Ludvigson's (2004) evidence that expected returns and expected dividend growth move together. It is useful to note that a negative reaction to aggregate earnings is entirely consistent with a positive reaction to firm earnings (a result confirmed in our data). The economic story is simple. Aggregate earnings fluctuate with discount rates because both are tied to macroeconomic conditions, while firm earnings primarily reflect idiosyncratic cash-flow news. As a result, the confounding effects of discount-rate changes show up only in aggregate returns. Put differently, cash-flow news is largely idiosyncratic while discount-rate changes are common across firms. By a simple diversification argument, discount-rate effects play a larger role at the aggregate level (see also Vuolteenaho, 2002; Yan, 2004). In short, our evidence suggests that common variation in discount rates explains an important fraction of aggregate stock market movements. The paper proceeds as follows. Section 2 provides background for our tests. Section 3 describes the data and the time-series properties of aggregate earnings. Section 4 studies the simple relation between returns and earnings, and Section 5 explores the correlations among returns, earnings, and other macroeconomic variables. Section 6 concludes. 2. Background: theory and evidence Our study relates to three areas of research: (1) empirical research on the stock market's reaction to earnings announcements; (2) a growing behavioral asset-pricing literature; and (3) research on the correlations among stock prices, business conditions, and discount rates. Prior research on post-earnings announcement drift, as well as recent behavioral theories, emphasize predictability in individual firm returns. Our study of aggregate price behavior provides a natural extension of this research.

The overall message from our analysis is, in some ways, quite simple: The market's reaction to aggregate earnings differs dramatically from its reaction to firm earnings. Taking all of the results together, we find little evidence that prices react slowly to aggregate earnings news. Recent behavioral theories that explain post-earnings announcement drift in firm returns do not seem to describe aggregate prices. We leave it to the reader to judge whether the results should be viewed as a rejection of the theories or simply evidence that they apply only at the firm level. At a minimum, our results suggest that recent behavioral models are incomplete because they provide little guidance for understanding why firm and aggregate price behavior should differ. Our results also provide new evidence on the connections among prices, earnings, discount rates, and business conditions. The strong negative reaction to aggregate earnings news suggests that discount rates rise when earnings are unexpectedly high, an effect that dominates the cash-flow news in quarterly and annual earnings. In fact, we do find that earnings are strongly correlated with changes in several proxies for discount rates, including T-bill rates, the term spread, and the default spread. However, these variables only partially explain the market's negative reaction to earnings news, which suggests that discount-rate shocks not captured by our proxies explain a significant fraction of returns (see also Fama, 1990; Campbell, 1991; Cochrane, 1992). The results are inconsistent with theoretical models that predict that discount rates and cash flows should move in opposite directions (see, e.g., Campbell and Cochrane, 1999; Chan and Kogan, 2002).