1. An image forming apparatus, comprising: a latent image bearer; a developing device configured to develop a latent image on the latent image bearer using a developer including a toner and a carrier; a toner density sensor configured to detect a toner density of the developer in the developing device; a supplier configured to supply the toner to the developing device; and a controller configured to control the supplier according to a detection result of the toner density by the toner density sensor and a toner density target value to adjust the toner density of the developer in the developing device, calculate a component adhesion deterioration degree that is a deterioration degree of the carrier due to adhesion of a toner component, obtained based on at least an average image area ratio of the output image, wherein the component adhesion deterioration degree increases as the average image area ratio increases, and calculate a coating abrasion deterioration degree that is a progression degree of deterioration due to coating abrasion of the carrier, obtained based on at least the average image area ratio of the output image, wherein the coating abrasion deterioration degree increases as the average image area ratio decreases, and correct the toner density target value and imaging condition affecting a toner adhesion amount of an output image separately from correcting the toner density, and based on the calculated component adhesion deterioration degree and the calculated coating abrasion deterioration degree.