Since the very beginning of the International Supercomputer Conference (ISC) series, one important focus has been the analysis of the supercomputer market. For 20 years, statistics about this marketplace have been published at ISC. Initially these were based on simple market surveys and since 1993, they are based on the TOP500 project, which has become the accepted standard for such data. We take the occasion of the 20th anniversary of ISC to combine and extend several previously published articles based on these data. We analyze our methodologies for collecting our statistics and illustrate the major developments, trends and changes in the High Performance Computing (HPC) marketplace and the supercomputer market since the introduction of the Cray 1 system.