I would like to ask your source for this. I find ridiculous that more than half of the population of Puerto Rico lives in San Juan. Yes, I know it's the capital and all, but I find that ridiculous
I'm pretty sure the population you put in for San Juan is the population of the Greater San Juan Metropolitan Area, which includes around 30 other cities besides San Juan (including a lot that are included in the answers). The actual population of San Juan is somewhere between 400k-500k