According to the GfK MRI Fall 2016 Survey of the American Consumer®, cell-phone only households make up 52% of households. Its even up to 23% for people aged 65+, which is the age group most likely to still have a land-line. Among the Millennials, cell-phone only households are up to 71%. This means that any phone survey is going to have to include cell phones, or it is probably not a valid sample.

The survey is based on 24,000 interviews of adults 18+. More background on the survey is here, while you can find some news coverage here.