According to the narrator, besides the economic advantages of his proposal, what is: another important advantage? better education fewer runaways more unskilled workers an inducement to marriage

Based on the given situation, the best answer for this would be:

an inducement to marriage

This is referred to Jonathan’s Swift’s ironic proposal of offering babies as food for an inducement of marriage, this writer had used situational irony to make a laughable reason to the audience of how drastic decisions can be.