Who controls the supply for coffee shops and based on what factors?

Besides the high demand and cost for gasoline these days, coffee is considered the second most traded commodity on worldwide markets next to oil. "Coffee is grown in more than 50 countries in a band around the equator and provides a living for more than 20 million farmers. Altogether, up to 100 million people worldwide are involved in the growing, processing, trading and retailing of the product" (Spilling the Beans,). In 2001, coffee farmers and plantations produced over 15 billion pounds of coffee while the world market only bought 13 billion pounds. The overproduction in the coffee industry is not a usual thing and is one of the major reasons why prices vary throughout the industry.