The way of generating data about population

I have to generate 100 rows of population of the cities and then also generate same number of rows of unemployed for each city. Data should be close to the real thing. My question is how to do that properly?.I have an ideaa and I want to share with you to get your opinion. For example:

I will take 200 rows of true population data in specific cities from Central Statistical Office and then randomly choose only 100 from these 200 rows. After that I will generate also randomly data about unemployed but based on earlier population data.

At this moment I have randomly generated data of the range from 1000 to 30 000 (for population) like this:

int random_population_result = (rand() % 29000) + 1000;

and unemployed range from 100 to 2000

int random_unemployed_result = (rand() % 1900) + 100;

but my professor said to me that isn't good idea to generate this kind of data in that way so he made me think about it. I introduced you my new idea above and I'm curious of your opinions.

Regards.