The primary reason for the OECD to propose a common list of sectors of economic activities reporting to PRTRs was to increase the comparability of data derived from various existing PRTR systems. Moreover, comparability would be enhanced if newly established systems cover the same sectors as existing systems. For these purposes, a comprehensive list of all reporting sectors (“Long Reporting Sector List”) and a harmonised list of sectors ("Short Reporting Sector List") were developed using the lists of sectors covered by five different PRTR systems, and those sectors recommended in the UNECE Kiev Protocol on PRTRs.