The growth of American industry raised the standard of living for most. It also created sharper economic and class divisions. The wealthiest 10% controlled 90% of wealth. The growth of large corporations introduces the need for thousands of white collar workers. Industrialization creates jobs for accountants, clerical workers, and salesmen. It also increases demand for services from doctors, lawyers, public employees and storekeepers. Two-thirds of Americans work for wages of about 10 hrs a day, 6 days a week. The wages are determined by laws of supply and demand. Due to the large available labor pool, most wages were barely above substantial level. David Ricardo's famous “iron law of wages” argues that raising wages promptly would simply increase the working population, and the availability of more workers would cause wages to fall, therefore creating a cycle of misery and starvation.