We propose a Kronecker product model for correlation or covariance matrices in thelarge dimensional case. The number of parameters of the model increases logarithmicallywith the dimension of the matrix. We propose a minimum distance (MD) estimator basedon a log-linear property of the model, as...

We devise a new high-frequency covariance matrix estimator based on price durations which is guaranteed to be positive-definite. Both non-parametric and parametric versions are proposed. A comprehensive Monte Carlo simulation shows that this class of estimators are less biased, more efficient,...

This paper studies the estimation of dynamic covariance matrices with multiple conditioning variables, where the matrix size can be ultra large (divergent at an exponential rate of the sample size). We introduce an easy-to-implement semiparametric method to estimate each entry of the covariance...

This paper proposes a new nonparametric spectral density estimator for time series models with general autocorrelation. The conventional nonparametric estimator that uses a positive kernel has mean squared error no better than n. We show that the best implementation of our estimator has mean...