Marketing is constantly changing in response to changes in customers, competitors, technology and regulations. Fewer than one third of the top 500 companies from 1957 still exist today due to this constant change. To succeed, companies must continually monitor changes in the market and respond through changes to their own marketing. Marketing involves understanding customer needs and wants in order to develop products and services to meet those needs, while effectively communicating to customers. Both an art and a science, marketing requires planning, segmentation, targeting, positioning and organization-wide involvement to be effective over the long term.