The Modern Language Association, 8th ed. does not have formal reference guidelines for datasets. An appropriate reference entry can be constructed using the MLA core elements.
Datasets (constructed using the MLA core elements):
Smith, Tom W., Peter V. Marsden, and Michael Hout. General Social Survey, 1972-2010 Cumulative File. ICPSR31521-v1. Chicago, IL: National Opinion Research Center [producer]. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], 2011. Web. 23 Jan 2012. doi:10.3886/ICPSR31521.v1.
MLA does, however, have formal guidelines for citing graphically represented data.
Goldberg, David, et al. Enrollments in Languages Other Than English in United States Institutions of Higher Education, Fall 2013. Modern Language Association, Feb 2015, www.mla.org/enrollments_census.