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Changes in coverage are a key driver of changes in the patent rights of the top three quintiles. In the top quintile, the increase in coverage reflects the expansion of patentable subject matter to software and biotechnology. In the second and middle quintiles, the increase in coverage is due to the allowing of pharmaceutical, food, and chemical patents. In contrast, the increase in coverage is small in the bottom quintile since a number of countries in this group have not (yet) extended patent protection to pharmaceutical and chemical patents. In summary, similarities and differences exist in the sources of change in patent rights by level of economic development. For all income groups, increases in membership in international agreements and enforcement mechanisms are key sources of change in patent rights, while increases in duration are a limited source. The main difference among income groups is that an expansion in patentable subject matter is observed primarily among the richest 60% of countries. Why this is so is worth researching further. One possible reason that higher income economies are more apt to expand coverage is that they possess a relatively greater capacity to innovate in more differentiated fields of invention. The legal authorities, from this perspective, accommodate the increased demand for patent protection in growing fields or industries.