What change has occurred in cities that switched from at-large to single-member districts?

The transition from at-large voting systems to single-member districts typically leads to an increase in representation for minority candidates. In at-large systems, candidates must appeal to a broader electorate, which can disadvantage those from minority groups who may be a smaller portion of the overall population but have concentrated support in specific areas.

Single-member districts allow for the creation of electoral boundaries that can reflect the demographic composition of a city more accurately. This setup makes it easier for minority candidates to win elections by concentrating their support within specific neighborhoods, which can help them secure enough votes to win a seat on the city council.

Thus, the correct answer indicates that cities that have switched to single-member districts have observed a significant increase in the election of minority candidates to the city council, which enhances overall representation and diversity in government.