Recent progress in the measuring techniques based on a combination of a quasistatic P-V analysis, conventional dynamic hysteresis measurements, and fast pulse characterization allows to determine the coercive voltage as a function of the frequency over a range of more than seven orders of magnitude. In this review, we explain the experimental techniques and present the results for the thin film systems of SrBi2Ta2O9 (SBT) and Pb(ZrTi)O3 (PZT). Theoretical models of the correlation between the ferroelectric relaxation and the coercive voltage are discussed in the light of the new data.