[en] We compute the production rate of photons in the ionizing Lyman continua (LyC) of H I (λ ≤ 912 Å), He I (λ ≤ 504 Å), and He II (λ ≤ 228 Å) using recent stellar evolutionary tracks coupled to a grid of non-LTE, line-blanketed WM-basic model atmospheres. The median LyC production efficiency is Q _LyC = (6 ± 2) × 10⁶⁰ LyC photons per M _☉ of star formation (range [3.1-9.4] × 10⁶⁰), corresponding to a revised calibration of 10^{53.3 ± 0.2} photons s^–1 per M _☉ yr^–1. Efficiencies in the helium continua are $Q_{\mathrm{H}\mathrm{e}\mathrm{I}}\approx <!--\; ???\; -->{10}^{60}$ photons $M_{\odot <!--\; ???\; -->}^{-<!--\; ???\; -->1}$ and $Q_{\mathrm{H}\mathrm{e}\mathrm{I}\mathrm{I}}\approx <!--\; ???\; -->{10}^{56}$ photons $M_{\odot <!--\; ???\; -->}^{-<!--\; ???\; -->1}$ at solar metallicity and larger at low metallicity. The critical star formation rate needed to maintain reionization against recombinations at z ≈ 7 is ${\stackrel{\dot{}<!--\; ??\; -->}{\mathrm{\rho <!--\; ??\; -->}}}_{\mathrm{S}\mathrm{F}\mathrm{R}}=(0.012M_{\odot <!--\; ???\; -->}{\mathrm{y}\mathrm{r}}^{-<!--\; ???\; -->1}{\mathrm{M}\mathrm{p}\mathrm{c}}^{-<!--\; ???\; -->3})[(1+z)/8{]}^3(C_{\mathrm{H}}/3)(0.2/f_{\mathrm{e}\mathrm{s}\mathrm{c}})$ for fiducial values of the intergalactic medium (IGM) clumping factor C _H ≈ 3 and LyC escape fraction f _esc ≈ 0.2. The boost in LyC production efficiency is an important ingredient, together with metallicity, C _H, and f _esc, in assessing whether IGM reionization was complete by z ≈ 7. Monte Carlo sampled spectra of coeval starbursts during the first 5 Myr have intrinsic flux ratios of F(1500)/F(900) ≈ 0.4-0.5 and F(912^–)/F(912⁺) ≈ 0.4-0.7 in the far-UV (1500 Å), the LyC (900 Å), and at the Lyman edge (912 Å). These ratios can be used to calibrate the LyC escape fractions in starbursts.