For Chicago you would include up to three authors in your footnote and final bibliography – bibliographic reference example:

Oswald, Andrew J, Eugenio Proto, and Daniel Sgroi, “Happiness and Productivity,” Journal of Labor Economics 33 (2015): 789-822. JSTOR.

If your reference has four or more authors, you can then use et al. (meaning ‘and others’) in your footnote – footnote example:

1. Sue Hobbs et al., Academic Skills: Listening, Speaking, and Study Skills (Oxford: Oxford University Press, 2011), 44.

List all for up to 10 authors in your bibliography; if there are more than 10 authors, list the first 7 followed by et al.