= Solution
Interpret the quoted values as the paper's 2006-era rounded cosmological benchmark. The <Hubble constant> is the present slope of the <Hubble law>, $v\simeq H_0d$ at sufficiently small <redshift>. A <cosmic distance ladder> begins with geometrical distance anchors, calibrates the <Cepheid period-luminosity relation> of <Cepheid variables>, and uses those distances to calibrate secondary indicators such as <Type Ia supernovae>. Distances to objects far enough away that <peculiar velocities> are a small fraction of recession velocity then determine the slope. Extinction, metallicity effects, distance-anchor calibration, sample selection and <peculiar velocities> contribute to its uncertainty.
The https://arxiv.org/abs/astro-ph/0012376[Hubble Space Telescope Key Project final result] was $H_0=72\pm8\ {\rm km\,s^{-1}\,Mpc^{-1}}$, combining random and systematic uncertainty, supporting the rounded value $70$. Independent approaches include distances inferred from gravitational-lens time delays and from cluster X-ray and <Sunyaev-Zeldovich effect> measurements; each brings different model uncertainties. Joint fits to the <cosmic microwave background> and large-scale structure also constrain $H_0$ within an assumed cosmological model. Thus \b[the evidence for a value near $70$ combines calibrated distances with independent cross-checks]; the approximate precision in the question should not be read as an identical uncertainty for every method.
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