Abundances of (a) ⁴He, (b) D, (c) ³He, and (d) ⁷Li as a function of ﹩\eta _{10}\equiv 10^{10}\eta ﹩, where η is the baryon‐to‐photon number ratio, as given by the standard hot big bang nucleosynthesis model. The theoretical dependences (solid lines) with 1 σ deviations (dashed lines) are from Fiorentini et al. (1998). The abundances of D, ³He, and ⁷Li are number ratios relative to H. For ⁴He, the mass fraction Y is shown. Our value ﹩Y_{p}=0.2452\pm 0.0015﹩ gives ﹩\eta =4.7^{+1.0}_{-0.8}\times 10^{-10}﹩, as shown by the solid vertical line. We show other data with 1 σ boxes.