confirmed that the cumulative fraction of CEMP stars strongly increases with decreasing metallicity. Overall, the cumulative fraction of CEMP stars rises from $\sim$ 20 % for \[Fe/H\] $< -2.0$, 30% for \[Fe/H\] $< -3.0$, 40% for \[Fe/H\] $< -3.5$, and 75% for \[Fe/H\] $<
-4.0$, after the inclusion of a carbon-normal star with [\[Fe/H\]]{} $\sim
-5.0$ (Beers & Christlieb 2005; Marsteller et al. 2005; Rossi et al. 2005; Frebel et al. 2006; Lucatello et al. 2006; Norris et al. 2007, 2013; Carollo et al. 2012; Spite et al. 2013; Yong et al. 2013).

The high frequency of CEMP stars at low metallicity indicates that a large amount of carbon (relative to iron) was produced at an early evolutionary stage of the Milky Way. Other evidence for the large production of carbon at early times comes from the discovery by Cooke et al. (2011) of an extremely metal-poor (EMP; \[Fe/H\] $\sim –3.0$) damped Ly-$\alpha$ (DLA) system at $z = 2.3$ that exhibits enhanced a carbon abundance ratio (\[C/Fe\]$ = +1.5$) and other elemental-abundance signatures similar to the CEMP-no class of stars. This classification (defined by Beers & Christlieb 2005) describes CEMP stars with no strong enhancements of $s$-process elements. Matsuoka et 