Why do working-class people so rarely go on to hold elected office in the world’s democracies? In this chapter, we review what scholars know and use new data on the social class backgrounds of national legislators in the OECD to evaluate several country-level explanations that have never been tested before in a large sample of comparative data. Our findings suggest that some hypotheses have promise and warrant future research: working-class people more often hold office in countries where labor unions are stronger and income is distributed more evenly. However, some common explanations do not pan out in our data – neither Left-party strength nor proportional representation is associated with working-class officeholding – and the various country-level explanations scholars have discussed in the past only account for at most 30 percent of the gap between the share of workers in the public and in national legislatures. Future research should focus comparative analyses on individual- and party-level explanations and consider the possibility that there are factors common to all democracies that limit working-class officeholding.