1. Hubble's draftsman made an error while preparing his famous diagram. From Figure 1 of his paper (http://adsabs.harvard.edu/abs/1931ApJ....74...43H), you'll notice that the vertical axis is in "km" rather than "km/sec."
2. Measurements of the Hubble Constant over time: http://www.pnas.org/content/101/1/8/F2.large.jpg For some reason it's not plotted logarithmically so it's hard to see the convergence towards ~70 km/s/Mpc in the last twenty years.
Interestingly, there was a long fight in the field of cosmology from ~1960 until ~1990 as to whether the Hubble constant was 50 or 100. It wasn't until within the past twenty years or so that the community began to agree upon the now-accepted value of ~70 km/s/Mpc.
1. Hubble's draftsman made an error while preparing his famous diagram. From Figure 1 of his paper (http://adsabs.harvard.edu/abs/1931ApJ....74...43H), you'll notice that the vertical axis is in "km" rather than "km/sec."
2. Measurements of the Hubble Constant over time: http://www.pnas.org/content/101/1/8/F2.large.jpg For some reason it's not plotted logarithmically so it's hard to see the convergence towards ~70 km/s/Mpc in the last twenty years.