Coal being then the chief source of power, much industrial reconstruction depended on there being a plentiful and cheap supply. But the newly nationalized industry was not doing well. Productivity failed to increase in step with increases in mechanization. Men were leaving the mines in large numbers for more attractive opportunities in the factories. Among those who remained, absenteeism averaged 20 percent. Labor disputes were frequent despite improved conditions of employment. Some time earlier the National Coal Board had asked the Institute to make a comparative study of a high producing, high morale mine and a low producing, low morale, but otherwise equivalent mine.