Electronic ordering and disorder effects in the pseudogap state of YBa$_{2}$Cu$_{3}$O$_{y}$

We report NMR measurements in the normal state of underdoped YBa$_{2}$Cu$_{3}$O$_{y}$. While unambiguous indication of charge-density-wave ordering is found in the pseudogap state, we interpret this as short range CDW order nucleated around native defects. We discuss the connections of this result to the initial evidence of CDW order in YBa$_{2}$Cu$_{3}$O$_{y}$ from NMR in high magnetic fields, to the more recent X-ray scattering data in the normal state as well as to a wider body of experimental results which have been considered to characterize the pseudogap state.