Here are Nielsen's highlights from its analysis of convention coverage:
Nearly two thirds of all U.S. households (64.5% or 73.2 million homes) tuned into at least one of the 2008 political conventions. This is about 120.1 million people. Viewership levels for the two conventions were essentially tied, with about half of all households watching each one.
15.0% of all households tuned to just the RNC, and 15.7% tuned to just the DNC. Another 33.9% of all households tuned to both conventions.
Homes that watched both conventions were more likely to be headed by someone 65 years or older. They also completed the most formal education: nearly one-third (32.3%) graduated from college. Those watching only one convention were fairly comparable on both education and HOH age, within a point or two.
Homes that only tuned to the RNC were more likely to have higher incomes ($100K+), to have a larger household size (4+), to be white, to own a DVR, and to have a head of household with higher education (4+ yrs college) and aged 35-54.
Homes that only tuned in to the DNC were more likely to have a lower income (<20K), to have a smaller household size (2), to be African American, and to have a head of household who is younger (<35) and who has less education (1-3 Yrs College).
About one-fifth (21.2%) of the DNC-only homes were headed by an African American. 83.5% of the RNC-only homes were headed by someone who is white.
Over 70% of African American homes tuned to at least one of the conventions, including 35.7% that tuned into both, more than each of the other ethnic breaks. Meanwhile 27.4% tuned in only to the DNC and 8.1% tuned in only to the RNC.
White homes had the second highest reach to both conventions (34.5%), and were the only ethnic break to have a higher percentage of partisan tuning to the RNC (16.2%) than the DNC (13.6%).
You can find the full report here.