The Efficiency Market Hypotheses (EMH) imply rational investors and no asset mispricing in the medium run. This paper critically evaluates on the point of whether an asset price bubble is an irrational phenomenon that cannot be detected. Thereby, I review the existing literature and reflect on...

This study presents and empirically tests a simple framework that examines the effects of market liquidity (the ease with which stocks are traded) and funding liquidity (the ease with which market participants can obtain funding) on stock market bubbles. Three key findings emerge from this...

We develop a novel machine learning method to estimate large dimensional time-varying GMM models via our newly designed ridge fusion regularization scheme. Our method is a one-step procedure and allows for abrupt, smooth and dual type time variation with a fast rate of convergence. It...

We propose a consistent and computationally efficient 2-step methodology for the estimation of multidimensional non-Gaussian asset models built using Lévy processes. The proposed framework allows for dependence between assets and different tail-behaviors and jump structures for each asset. Our...

Dynamic average correlations of stock returns are predicted by the volatility of the market excess return and moving average returns of value, size and momentum portfolios. While the influence of market volatility on average correlation is well-known, the role of value, size and momentum appears...

We propose new systematic tail risk measures constructed using two different approaches. The first extends the canonical downside beta and co-moment measures, while the second is based on the sensitivity of stock returns to innovations in market crash risk. Both tail risk measures are associated...

We develop a penalized two-pass regression with time-varying factor loadings. The penalization in the first pass enforces sparsity for the time-variation drivers while also maintaining compatibility with the no arbitrage restrictions by regularizing appropriate groups of coefficients. The second...

The influence of past stock price movements on volatilities and correlations is essential for understanding diversification and contagion in financial markets. We develop a model that makes the influence of past returns on volatilities and correlations explicit. Employing information about...