The article examines why wages are higher in cities compared to rural areas, focusing on how different factors affect wages for both skilled and unskilled workers. By studying migrants in Italy, the researchers found that unskilled workers see their wages increase over time due to gaining more skills, while skilled workers benefit from both higher initial wages and wage growth. This suggests that for unskilled workers, learning new skills is key to wage growth, while for skilled workers, being in a city where coordination is easier leads to higher wages.