This thesis consists of two parts. The first part contributes statistical methodology for nonnegative integer-valued time series. The second part of this thesis consists of two chapters. One chapter is concerned with the development of efficient estimators of the marginal distribution functions...

In this paper we study the zero frequency spectral properties of fractionally cointegrated long memory processes and introduce a new frequency domain principal components estimator of the cointegration space and the factor loading matrix for the long memory factors. We find that for fractionally...