What major socio-economic practice, contributing to the expansion of commoner surnames and social mobility, characterized the late Joseon Dynasty?

💡 Explanation:

The Joseon government, particularly after major conflicts like the Imjin War, widely sold official positions and noble 'yangban' status to raise funds. This commercialization eroded the rigid class hierarchy, allowing commoners to acquire status and the right to adopt surnames, thereby increasing social mobility.