The Spurious Effect of ARCH Errors on Linearity Tests:A Theoretical Note and an Alternative Maximum Likelihood Approach

Linearity tests against smooth transition nonlinearity are typically based on the standard least-squares (LS) covariance matrix estimator. We derive an expression for the bias of the LS estimator in the presence of ARCH errors. We show that the bias is downward, and increases dramatically with the persistence of the variance process. As a consequence, conventional tests spuriously indicate nonlinearity. Next, we examine an alternative maximum likelihood approach. Our findings suggest that this approach has substantially better size properties than tests based on least-squares and heteroskedasticity-consistent matrix estimators, and performs comparably to a bootstrap technique

Bubbles in House Prices and their Impact on Consumption: Evidence for the US

This paper provides evidence that some aggregate and regional U.S. real house price indices exhibited a bubble in the last few years according to the Phillips et al. (2007) unit root test. We subsequently investigate whether house price acceleration (deceleration) had a signi.cant impact on consumption in an error correction mechanism implied by a wide class of optimizing models. Our results support the argument that real house prices have their major effect on consumption only during the bubble period

Nonlinear Econometric Methods in International Economics.

This thesis builds upon recent developments in the areas of international economics, econometrics and computational statistics, to provide a robust framework for specifying, modelling and forecasting real exchange rates. The main research topics addressed are the following. First, the impact of conditional heteroskedas-ticity on linearity tests. Second, the parsimonious modelling and forecasting of the dollar-sterling real exchange rate using a long span of data. Third, the reexamination of the well-documented real exchange rate-consumption anomaly from the viewpoint of nonlinear dynamics. Finally, the relationship between real exchange rate persistence and time-varying trade costs

Bubbles and Crashes : A Tale of Quantiles

Periodically collapsing bubbles, if they exist, induce asymmetric dynamics in asset prices. In this paper, I show that unit root quantile autoregressive models can approximate such dynamics by allowing the largest autoregressive root to take values below unity at low quantiles, which correspond to price crashes, and above unity at upper quantiles, that correspond to bubble expansions. On this basis, I employ two unit root tests based on quantile regressions to detect bubbles. Monte Carlo simulations suggest that the two tests have good size and power properties, and can outperform recursive least-squares-based tests that allow for time variation in persistence. The merits of the two tests are further illustrated in three empirical applications that examine Bitcoin, U.S. equity and U.S. housing markets. In the empirical applications, special attention is given to the issue of controlling for economic fundamentals. The estimation results indicate the presence of asymmetric dynamics that closely match those of the simulated bubble processes

House prices, (un)affordability and systemic risk

This is the first paper to examine the role of the real estate sector and housing unaffordability in the determination of systemic risk. We measure the systemic risk of the UK by employing the ΔCoVaR method developed by Adrian and Brunnermeier [(2016). CoVaR. American Economic Review, 106(7), 1705–1741] and we explore both its cross-sectional and time series behaviour. Regarding the former, we show that when the real estate sector is under distress the tail risk of the entire financial system increases significantly. With respect to the latter, the findings of our dynamic model suggest that sustainable house prices positively contribute to the stability of the financial sector; whilst house price exuberance and rapid increases in housing unaffordability amplify systemic risk. Finally, we examine the conjecture that the banking sector comprises a transmission channel from the housing market to systemic risk. Our empirical results are in line with this argument and highlight the key role of housing unaffordability

Testing for linear and nonlinear Granger Causality in the real exchange rate-consumption relation

International real business cycle models predict a relationship between real exchange rates and consumption. This prediction is not supported by the empirical literature. In a new approach, we apply nonlinear Granger-causality tests to data for 14 OECD countries

A nonlinear analysis of the real exchange rate-consumption relationship

A variety of international macroeconomic models predict a relationship between the real exchange rate and consumption. The empirical evidence in favor of such a relationship is limited, the so-called Backus and Smith puzzle. In this paper, we extend the analysis to allow for nonlinear dynamics and volatility changes across exchange rate regimes. Our findings suggest that long-run relationships in line with standard international business cycle models do exist for many Organization for Economic Co-operation and Development (OECD) countries. Further, Monte Carlo experiments illustrate that the nonlinear models can generate the Backus and Smith and the exchange rate disconnect puzzles. In this paper, we also contribute to the nonlinear real exchange rate literature by establishing a theoretical relationship between volatility and persistence. In accordance with the theoretical results, our empirical findings suggest that the increase in volatility in the post-Bretton Woods era is associated with relatively fast mean reversion of the real rate toward its equilibrium value

Modeling changes in U.S. monetary policy

The monetary economics literature has highlighted four issues that are important in evaluating U.S. monetary policy since the late 1960s: (i) time variation in policy parameters, (ii) asymmetric preferences, (iii) revisions to economic data, and (iv) heteroskedasticity. This paper, for the first time, estimates a Taylor rule model that addresses these four issues simultaneously. Our findings suggest that U.S. monetary policy has experienced substantial changes in terms of both the response to inflation and to real economic activity, as well as changes in preferences. These changes cannot be captured adequately by a single structural break at the late 1970s, as has been commonly assumed in the literature, and play a non-trivial role in economic performance

exuber:Recursive Right-Tailed Unit Root Testing with R

This paper introduces the R package exuber for testing and date-stamping periods of mildly explosive dynamics (exuberance) in time series. The package computes test statistics for the supremum ADF test (SADF) of Phillips, Wu, and Yu (2011), the generalized SADF (GSADF) of Phillips, Shi, and Yu (2015a,b), and the panel GSADF proposed by Pavlidis, Yusupova, Paya, Peel, Martinez-Garcia, Mack, and Grossman (2016); generates finite-sample critical values based on Monte Carlo and bootstrap methods; and implements the corresponding date-stamping procedures. The recursive least-squares algorithm that we introduce in our implementation of these techniques utilizes the matrix inversion lemma and in that way achieves significant speed improvements. We illustrate the speed gains in a simulation experiment, and provide illustrations of the package using artificial series and a panel on international house prices