1. A degradation compensation apparatus, comprising: a calculator provided with gray data regarding a plurality of consecutive frames and configured to calculate and output a frame degradation amount of a current frame, which indicates a degree of degradation of the current frame; a memory configured to accumulate and store the frame degradation amount of the current frame and to output a cumulative degradation amount, which is an accumulated degree of degradation of frames up to the current frame; and a data corrector configured to correct the gray data for a subsequent frame based on the cumulative degradation amount, wherein: each of the plurality of consecutive frames comprises first and second blocks each comprising a plurality of pixels; the frame degradation amount of the current frame is calculated based on one of the pixels included in the first block and one of the pixels included in the second block; and the frame degradation amount of the current frame is calculated using different pixels from those used to calculate a frame degradation amount of a previous frame.