In this paper, we give a general time-varying parameter model, where the multidimensional parameter possibly includes jumps. The quantity of interest is defined as the integrated value over time of the parameter process Θ = T −1 T 0 θ * t dt. We provide a local parametric estimator (LPE) of Θ and conditions under which we can show the central limit theorem. Roughly speaking those conditions correspond to some uniform limit theory in the parametric version of the problem. The framework is restricted to the specific convergence rate n 1/2 . Several examples of LPE are studied: estimation of volatility, powers of volatility, volatility when incorporating trading information and time-varying MA(1). Keywords: integrated volatility; market microstructure noise; powers of volatility; quasi maximum likelihood estimator * We are indebted to Simon Clinet, Takaki Hayashi, Dacheng Xiu, participants of the seminars in Berlin and Tokyo and conferences in Osaka, Toyama, the SoFie annual meeting in Hong Kong, the PIMS meeting in Edmonton for valuable comments, which helped in improving the quality of the paper.We assume that we observe the d-dimensional vectors Z 0,n , · · · , Z Nn,n , where N n can be random, the observation times satisfy τ 0,n := 0 < τ 1,n < · · · < τ Nn,n ≤ T . The observations and the observation times are both related to the latent parameter θ * t . As an example, the observations can satisfy Z τ i,n ,n = X τ i,n + i,n , where X t = σ t dW t stands for the efficient price, W t is a standard Brownian motion, i,n corresponds to the market microstructure noise (which will be restricted to be of order i,n = O p (1/ √ n) due to the limitation of the technology developed in Section 3), is independent and identically distributed (IID) and independent from X t , and the latent parameter is equal to the volatility, i.e. θ * t = σ 2 t . We assume that the parameter process θ * t takes values in K, a (not necessarily compact) subset of R p . We do not assume any independence between θ * t and the other quantities driving the observations, such as the Brownian motion of the efficient price process. In particular, there can be leverage effect (see e.g. Wang and Mykland (2014), Aït-Sahalia et al. (2017)). Also, the arrival times τ i,n and the parameter θ * t can be correlated, i.e. there is (some kind of) endogeneity in sampling times.
AsymptoticsThere are commonly two choices of asymptotics in the literature: the high-frequency asymptotics, which makes the number of observations explode on [0, T ], and the lowfrequency asymptotics, which takes T to infinity. We choose the former one. Investigating the low-frequency implementation case is beyond the scope of this paper 1 .1 If we set down the asymptotic theory in the same way as in p.3 of Dahlhaus (1997), we conjecture that the results of this paper would stay true.