Shoes have evolved over time from simple sandals to complex designs that vary in style, material, and cost. The earliest known shoes date back 7,000-8,000 BC and were simple foot coverings to protect the feet. Contemporary shoes can be made of expensive materials through complex construction processes. A shoe industry incurs direct costs for labor, materials like leather and laces, and manufacturing overhead including indirect labor, utilities, supplies, and other costs like taxes, insurance, and equipment maintenance.