没有合适的资源?快使用搜索试试~ 我知道了~
该文章使用DSGE模型分析了股市的泡沫,对识别和评估股市泡沫有启发意义。
资源推荐
资源详情
资源评论
A Bayesian DSGE Model of
Stock Market Bubbles and Business Cycles
∗
Jianjun Miao
†
, Pengfei Wang
‡
, and Zhiwei Xu
§
September 28, 2012
Abstract
We present an estimated DSGE model of stock market bubbles and business cycles using
Bayesian methods. Bubbles emerge through a positive feedback loop mechanism supported by
self-fulfilling beliefs. We identify a sentiment shock which drives the movements of bubbles and
is transmitted to the real economy through endogenous credit constraints. This shock explains
more than 96 percent of the stock market volatility and about 25 to 45 percent of the variations in
investment and output. It generates the comovements between stock prices and macroeconomic
quantities and is the dominant force in driving the internet bubbles and the Great Recession.
Keywords: Stock Market Bubbles, Bayesian Estimation, DSGE, Credit Constraints, Business
Cycle, Sentiment Shock
JEL codes: E22, E32, E44
∗
We thank Paul Beaudry, Francisco Buera, Christophe Chamley, Simon Gilchrist, Timothy Kehoe, Bob King,
Alb erto Martin, Rachel Ngai, Vincenzo Quadrini, Harald Uhlig, Jaume Ventura, and Tao Zha for helpful comments.
We are especially grateful to Zhongjun Qu for numerous conversations and to Zheng Liu and Tao Zha for kindly
providing us with the data. We have also benefitted from comments from participants in the Boston University
Macro Workshop, 2012 AFR Summer Institute of Economics and Finance, and HKUST International Macroeconomics
Workshop. First version: April 2012.
†
Department of Economics, Boston University, 270 Bay State Road, Boston, MA 02215. Email: miaoj@bu.edu.
Tel.: 617-353-6675.
‡
Department of Economics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong. Tel:
(+852) 2358 7612. Email: pfwang@ust.hk
§
Department of Economics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong.
Email: zwxu@ust.hk. Tel.: (+852) 67334367.
1. Introduction
The U.S. stock market is volatile relative to fundamentals as is evident from Figure 1, which presents
the monthly data of the real Standard and Poor’s Composite Stock Price Index from January 1871
to January 2011, and the corresponding series of real earnings. Two recent boom-bust episodes are
remarkable. Starting from January 1995, the stock market rose persistently and reached the peak
in August 2000. Through this period, the stock market rose by about 1.8 times. This boom is often
attributed to the internet bubble. Following the peak in August 2000, the stock market crashed,
reaching the bottom in February 2003. The stock market lost about 47 percent. After then the
stock market went up and reaching the peak in October 2007. This stock market runup is often
attributed to the housing market bubble. Following the burst of the bubble, the U.S. economy
entered the Great Recession, with the stock market drop of 52 percent from October 2007 through
March 2009.
The U.S. stock market comoves with macroeconomic quantities. The boom phase is often
associated with strong output, consumption, investment, and hours, while the bust phase is often
associated with economic downturns. Stock prices, consumption, investment, and hours worked
are procyclical, i.e., they exhibit a positive contemporaneous correlation with output (see Table 3
presented later).
The preceding observations raise several questions. What are the key forces driving the boom-
bust episodes? Are they driven by economic fundamentals, or are they bubbles? What explains
the comovement between the stock market and the macroeconomic quantities? These questions
are challenging to macroeconomists. Standard macroeconomic models treat the stock market as
a sideshow. In particular, after solving for macroeconomic quantities in a social planner problem,
one can derive the stock price to support these quantities in a competitive equilibrium. Much
attention has been devoted to the equity premium puzzle (Hansen and Singleton (1983) and Mehra
and Prescott (1988)). However, the preceding questions have remained underexplored.
The goal of this paper is to provide an estimated dynamic stochastic general equilibrium (DSGE)
model to address these questions. To the best of our knowledge, this paper provides the first
estimated DSGE model of stock market bubbles using Bayesian methods. Our model-based, full-
information econometric methodology has several advantages over the early literature using the
single-equation or the vector autoregression (VAR) approach to the identification of bubbles. First,
because both bubbles and fundamentals are not observable, that literature fails to differentiate
between misspecified fundamentals and bubbles (see Gurkaynak (2008) for a recent survey). By
contrast, we treat bubbles as a latent variable in a DSGE model. The state space representation of
1
the DSGE model allows us to conduct Bayesian inference of the latent variables by knowledge of the
observable data. We can answer the question as to whether bubbles are important by comparing
the marginal likelihoods of a DSGE model with bubbles and an alternative DSGE without bubbles.
Second, the single-equation or the VAR approach does not produce time series of the bubble
component and the shock behind the variation in bubbles. Thus, it is difficult to evaluate whether
the properties of bubbles are in line with our daily-life experience. By contrast, we can simulate our
model based on the estimated parameters and shocks to generate a time series of bubbles. Third,
because our model is structural, we can do counterfactual analysis to examine the role of bubbles
in generating fluctuations in macroeconomic quantities.
We set up a real business cycle model with three standard elements: habit formation, invest-
ment adjustment costs, and variable capacity utilization. The novel element of our model is the
assumption that firms are subject to idiosyncratic investment efficiency shocks and face endogenous
credit constraints as in Miao and Wang (2011a,b, 2012a,b), and Miao, Wang, and Xu (2012). Under
this assumption, a stock market bubble can exist through a positive feedback loop mechanism sup-
ported by self-fulfilling beliefs. The intuition is as follows. Suppose that households have optimistic
beliefs about the stock market value of the firm. The firm uses its assets as collateral to borrow
from the lender. If both the lender and the firm believe that firm assets have high value, then the
firm can borrow more and make more investment. This makes firm value indeed high, supporting
people’s initial optimistic beliefs. Bubbles can burst if people believe so. By no arbitrage, a rational
bubble on the same asset cannot re-emerge after a previous bubble bursts. To introduce recurrent
bubbles in the model, we introduce exogenous entry and exit. New entrants bring new bubbles in
the economy, making the total bubble in the economy stationary.
We introduce a sentiment shock which drives the fluctuations in the bubble and hence the
stock price. This shock reflects households’ beliefs about the relative size of the old bubble to
the new bubble. This shock is transmitted to the real economy through the credit constraints. Its
movements affect the tightness of the credit constraints and hence a firm’s borrowing capacity. This
affects a firm’s investment decisions and hence output.
1
In addition to this shock, we incorporate six
other shocks often studied in the literature: persistent and transitory labor-augmenting technology
(or TFP) shocks, persistent and transitory investment-specific technology (IST) shocks, the labor
supply shock, and the credit shock. We estimate our model using Bayesian methods to fit the U.S.
data of consumption, investment, hours, the relative price of investment goods, and stock prices.
1
Stanley and Merton (1984), Barro (1990), Chirinko and Schaller (2001), Baker, Stein, and Wurgler (2003), Goyal
and Yamada (2004), Gilchrist, Himmelberg and Huberman (2005) find empirical evidence that investment responds
to the stock market value beyond the fundamentals. See Gan (2007) and Chaney, Sraer, and Thesmar (2009) for
empirical evidence on the relation between collateral constraints and investment.
2
Our full-information, model-based, empirical strategy for identifying the sentiment shock exploits
the fact that in the theoretical model the observable variables react differently to different types of
shocks. We then use our estimated model to address the questions raised earlier. We also use our
model to shed light on two major bubble and crash episodes: (i) the internet bubble during the
late 1990s and its subsequent crash, and (ii) the recent stock market bubble caused by the housing
bubble and the subsequent Great Recession.
Our estimation results show that the sentiment shock explains more than 96 percent of the
fluctuations in the stock price over various forecasting horizons. It is also the dominant force
in driving the fluctuations in investment in the medium run, explaining about 40 percent of its
variations. Overall, it explains about 25 to 45 percent of the variations in investment and output
over various horizons. Historical decomposition of shocks shows that the sentiment shock explains
almost all of the stock market booms and busts. In addition, it is the dominant driving force
behind the movements in investment during the internet bubble and crash and the recent stock
market bubble and the subsequent Great Recession. The sentiment shock accounts for a large share
of the consumption fall during the Great Recession. But it is not a dominant driver behind the
consumption movements during the internet bubble and crash. For both boom-bust episodes, the
labor supply shock, instead of the sentiment shock, is the major driving force behind the movements
in labor hours.
To see what drives the comovement between the stock market and the macroeconomic quanti-
ties, we compute counterfactual simulations of history from the model based on the estimated time
series of sentiment shocks. We then compute the impulse responses of the stock price, consumption,
investment, and hours following a shock to the stock price from a four-variable Bayesian vector au-
toregression (BVAR) based on the simulated data. We compare these responses to those estimated
from the actual data. We find that the impulse responses from the simulated data conditional on
the sentiment shock alone mimic those from the actual data, suggesting that the sentiment shock
is the major driver of the comovement.
The intuition behind the comovement is as follows. In response to a positive sentiment shock,
the bubble and stock price rise. This relaxes credit constraints and hence raises investment. But
Tobin’s marginal Q falls, causing the capacity utilization rate to rise. This induces the labor
demand to rise. The wealth effect due to the rise in stock prices causes consumption to rise and the
labor supply to fall. It turns out that the rise in the labor demand dominates the fall in the labor
supply, and hence labor hours rise. The increased hours and capacity utilization raises output.
In our model, the sentiment shock is an unobserved variable. We infer its properties from our
five time series of the U.S. data using an estimated model. Given its importance for the stock
3
market and business cycles, one may wonder whether there is a direct measure of this shock. We
find that the consumer sentiment index published monthly by the University of Michigan and
Thomson Reuters is highly correlated with our sentiment shock (the correlation is 0.61).
2
Thus,
this index can provide an observable measure of the sentiment shock in our model and should be
useful for understanding the stock market and business cycles.
It is challenging for standard DSGE models to explain the stock market booms and busts.
One often needs a large investment adjustment cost parameter to make Tobin’s marginal Q highly
volatile. In addition, one also has to introduce other sources of shocks to drive the movements
of the marginal Q b ecause many shocks often studied in the literature cannot generate either the
right comovements or the right relative volatility. For example, the TFP shock cannot generate
large volatility of the stock price, while the IST shock generates counterfactual comovements of
the marginal Q (hence stock prices) and the relative price of investment goods if both series are
used as observable data. The credit shock typically makes investment and consumption move in
an opposite direction and makes the marginal Q move countercyclically.
Recently, two types of shocks have drawn wide attention: the news shock and the risk (or
uncertainty) shock. The idea of the news shock dates back to Pigou (1926). It turns out that
the news shock cannot generate the comovement in a standard real business cycle model (Barro
and King (1984) and Wang (2012)). To generate the comovement, Beaudry and Portier (2004)
incorporate multisectoral adjustment costs, Christiano et al. (2008) introduce nominal rigidities
and inflation-targeting monetary policy, and Jaimovich and Rebelo (2009) consider preferences that
exhibit a weak short-run wealth effect on the labor supply. These three papers study calibrated
DSGE models and do not examine the empirical importance of the news shock.
3
Fujiwara, Hirose,
and Shintani (2011) and Schmitt-Grohe and Uribe (2012) study this issue using the Bayesian
DSGE approach. Most Bayesian DSGE models do not incorporate stock prices as observable data
for estimation. As Schmitt-Grohe and Uribe (2012) point out, “as is well known, the neoclassical
model does not provide a fully adequate explanation of asset price movements.”
4
By incorporating the stock price data, Christiano, Motto, Rostagno (2010, 2012) argue that the
risk shock, related to that in Bloom (2009), displaces the marginal efficiency of investment shock
and is the most important shock driving business cycles.
5
They also introduce a news shock to the
2
The consumer confidence index issued monthly by the Conference Board is also highly correlated with our
smo othed sentiment shock. The correlation is 0.5.
3
Beaudry and Portier (2006) study the empirical implications of the news shock using the VAR approach.
4
In Section 6.8 of their paper, Schmitt-Grohe and Uribe (2012) discuss briefly how the share of unconditional
variance explained by anticipated shocks will change when stock prices are included as observable data. But they do
not include stock prices in their baseline estimation.
5
It is difficult for shocks to the TFP shock’s variance (uncertainty shocks) to generate comovements among
investment, consumption, hours, and stock prices in standard DSGE models (see, e.g., Basu and Bundick (2011)).
4
剩余65页未读,继续阅读
资源评论
anqiangh
- 粉丝: 0
- 资源: 1
上传资源 快速赚钱
- 我的内容管理 展开
- 我的资源 快来上传第一个资源
- 我的收益 登录查看自己的收益
- 我的积分 登录查看自己的积分
- 我的C币 登录后查看C币余额
- 我的收藏
- 我的下载
- 下载帮助
安全验证
文档复制为VIP权益,开通VIP直接复制
信息提交成功