Utilitarianism: The Aggregation Question

Utilitarianism and other aggregationist moral theories view the public interest or the general welfare as an aggregate of individual goods. But critics of these theories question whether there is adequate justification for employing the concept of an aggregate social good. How are we supposed to sum up individual interests? Is it even possible to compare the utilities of different people or to assign values to individual utilities that can be added or subtracted? If not, how is the general good to be aggregated? Critics have also raised concerns about the aggregative approach in ethics-concerns about its implications for distributive justice, individual liberty, and democratic institutions.