This is a very important aspect of the study. They did not do a true randomized survey as participants were self-selecting (online surveys have this inherently -- well, mostly).
It's not clear that this was or wasn't a self-selecting sample. The article does state that the surveying was conducted online:
In the research, more than 6,000 U.S. working adults over the age of 18 were surveyed online by independent research firm Edelman Intelligence between July 29 — August 24, 2016. Among them, 2,049 were freelancers and 3,953 were non-freelancers. The survey defined freelancers as individuals who have engaged in supplemental, temporary, project- or contract-based work within the past 12 months.
dredmorbius|9 years ago
In the research, more than 6,000 U.S. working adults over the age of 18 were surveyed online by independent research firm Edelman Intelligence between July 29 — August 24, 2016. Among them, 2,049 were freelancers and 3,953 were non-freelancers. The survey defined freelancers as individuals who have engaged in supplemental, temporary, project- or contract-based work within the past 12 months.