Abundance ratio scatter with metallicity and r-process enrichment. Left panel: [Eu/Fe] ratios of all Milky Way and several dwarf galaxy stars with Eu detections from the SAGA Database as a function of metallicity [Fe/H]. An enormous scatter of more than two orders of magnitude exists for [Fe/H] < −2. Right panel: individual linear Sr/Eu ratios for all stars with [Fe/H] < −2.5 as a function of [Eu/Fe], which represents the r-process enrichment. A drastic reduction is seen for [Eu/Fe] > 0−0.3.