Area coverages for the six classes spanning the period March 1996–December 2012 for the EIT 171 Å bandpass (top left panel) and the EIT 195 Å bandpass (top right panel). The extent on the y-axis gives the area coverage for the corresponding class, with the six features summing to one. The classes are displayed from bottom to top in order of increased intensity values, from the coronal holes (Class 1, CH) up to the brightest part of an active region (Class 6, AR3). The bottom panels show a zoom-in of the area coverage of the coronal holes. The data gaps in the EIT and SEM data are due to the SOHO vacation in summer and fall of 1998.