Short-Term GDP Forecasting With a Mixed-Frequency Dynamic Factor Model With Stochastic Volatility

In this article, we develop a mixed frequency dynamic factor model in which the disturbances of both the latent common factor and of the idiosyncratic components have time-varying stochastic volatilities. We use the model to investigate business cycle dynamics in the euro area and present three sets of empirical results. First, we evaluate the impact of macroeconomic releases on point and density forecast accuracy and on the width of forecast intervals. Second, we show how our setup allows to make a probabilistic assessment of the contribution of releases to forecast revisions. Third, we examine point and density out of sample forecast accuracy. We find that introducing stochastic volatility in the model contributes to an improvement in both point and density forecast accuracy. Supplementary materials for this article are available online.     

Testing Nowcast Monotonicity with Estimated Factors

This article proposes a test to determine whether “big data” nowcasting methods, which have become an important tool to many public and private institutions, are monotonically improving as new information becomes available. The test is the first to formalize existing evaluation procedures from the nowcasting literature. We place particular emphasis on models involving estimated factors, since factor-based methods are a leading case in the high-dimensional empirical nowcasting literature, although our test is still applicable to small-dimensional set-ups like bridge equations and MIDAS models. Our approach extends a recent methodology for testing many moment inequalities to the case of nowcast monotonicity testing, which allows the number of inequalities to grow with the sample size. We provide results showing the conditions under which both parameter estimation error and factor estimation error can be accommodated in this high-dimensional setting when using the pseudo out-of-sample approach. The finite sample performance of our test is illustrated using a wide range of Monte Carlo simulations, and we conclude with an empirical application of nowcasting U.S. real gross domestic product (GDP) growth and five GDP sub-components. Our test results confirm monotonicity for all but one sub-component (government spending), suggesting that the factor-augmented model may be misspecified for this GDP constituent. Supplementary materials for this article are available online.     

大维变量选择、混频因子模型与新冠肺炎疫情冲击下的GDP现时预测

新冠肺炎疫情不仅对我国宏观经济造成了巨大冲击,也为准确预测我国宏观经济未来走势带来挑战。本文从新冠肺炎疫情冲击出发,将模型置信集检验与U-MIDAS模型组合,设计了一种在混频情形下利用预测变量的异质性波动从大维数据集中选取对GDP具有稳定预测效果变量的方法。通过利用选取出的稳定性变量构建多种形式的混频目标因子模型并与其他类型的混频因子模型对比,全面评估了不同模型在疫情前后对GDP进行高频现时预测的效果。研究发现,在疫情冲击前的平稳时期,利用覆盖范围较广的变量构建双因子MIDAS模型预测效果最优;利用稳定性变量构建的单因子U-MIDAS模型同样具有良好的预测效果。当经济从冲击中持续恢复时,利用部分稳定性变量构建的双因子U-MIDAS模型在捕捉到GDP的核心变化后率先对其连续做出准确的现时预测。经济稳定时,对预测变量设定较长的滞后阶数会提升预测效果;在冲击后的恢复期中则应减少滞后阶数,避免变量在冲击中出现的异常值对预测产生负面影响。本文也为当经济受到巨大外生冲击或处于冲击后的恢复期时其他宏观经济指标的预测提供了有价值的参考。     

Combined Density Nowcasting in an Uncertain Economic Environment

We introduce a combined density nowcasting (CDN) approach to dynamic factor models (DFM) that in a coherent way accounts for time-varying uncertainty of several model and data features to provide more accurate and complete density nowcasts. The combination weights are latent random variables that depend on past nowcasting performance and other learning mechanisms. The combined density scheme is incorporated in a Bayesian sequential Monte Carlo method which rebalances the set of nowcasted densities in each period using updated information on the time-varying weights. Experiments with simulated data show that CDN works particularly well in a situation of early data releases with relatively large data uncertainty and model incompleteness. Empirical results, based on U.S. real-time data of 120 monthly variables, indicate that CDN gives more accurate density nowcasts of U.S. GDP growth than a model selection strategy and other combination strategies throughout the quarter with relatively large gains for the two first months of the quarter. CDN also provides informative signals on model incompleteness during recent recessions. Focusing on the tails, CDN delivers probabilities of negative growth, that provide good signals for calling recessions and ending economic slumps in real time.