16 Tons, a song written by Merle Travis, focused on the hardships of working in a mine, which are embodied in the verse "I owe my sould to the company store." This referrs to when mines would pay their employees with vouchers that could only be redeemed at the "company store," which the mine owned. Similarly today, companies like Wal-Mart would pay their employees in prepaid cards instead of paychecks to make money on fees. Both methods exploited already precarious work for the company's economic benefit. This economic exploitation is also one of the causes of precarious work. If a company can find someone else who will do the work cheaper, and quicker then they will. Companies no longer invest in their employees. Rather, it seems that today it is the employee who invests in the company.