Child Labor in the european coal industry

This graph contains many different types of info including what types of people made up the work force. I see that the green(females under 15) has the smallest number of people in every year. this means that they used less younger woman probably for strength purposes. I also see that the blue character (males 15 to 20) is the biggest category every year. I think this means that the work was more physically demanding that they needed these men for. Ultimately this shows that the work force increase massively i assume due to factory production.