Top panel: sources of electron capture and positron decay ( β⁺) reaction rates in our reaction network. The labels are as follows: VITAL (only ⁷Be + e⁻→⁷Li + ν + γ from Caughlan & Fowler 1988); NETB1 (weak reaction rates from NetGen – http://www.astro.ulb.ac.be/Netgen – which are predominantly from Takahashi & Yokoi 1987 and Goriely 1999); ODA94 (Oda et al. 1994); FFN85 (Fuller et al. 1985); LMP00 (Langanke & Martínez-Pinedo 2000); NKK04 (Nabi & Klapdor-Kleingrothaus 2004); JINAC (Cyburt et al. 2010). Bottom panel: same as top panel; shaded regions cover isotopes with mass fraction greater than X = 5 × 10⁻⁶ for an NSE state at T = 9 GK and ρ = 10¹⁰ g cm⁻³. The value of Y_e for each shaded region is written on the enclosing contour line. One can see that at Y_e = 0.45 there are a substantial number of isotopes outside of the region covered by the Langanke & Martínez-Pinedo (2000) tables with mass fractions greater than X = 5 × 10⁻⁶, indicating that they could potentially contribute to the evolution of Y_e when their weak reaction rates are considered, which is what we observe in our simulations when including the Nabi & Klapdor-Kleingrothaus (2004) rates.