A test score that has been standardized over time, across subjects, across schooling levels, and across various international and regional assessments. It is calculated by creating a ratio between U.S. scores averaged across subjects and over schooling level on all international tests (such as PISA and TIMSS) to average scores averaged across subjects and over schooling levels on the U.S. National Assessment of Educational Progress (NAEP) approximated to the nearest 5-year time step from 1965-2010. All raw international scores are averaged across subjects and over school levels and approximated to the nearest 5-year interval, averaged across tests, and then multiplied by this ratio. This makes these adjusted scores comparable over time, across countries and across international tests. Test scores from countries which only participate in regional assessments are included in the above transformation after being averaged across subjects and over schooling levels and then multiplied by a ratio comparing average scores across subjects and schooling levels in a given regional test and average scores across subjects and schooling levels on an international assessment for all doubloon countries - countries which participate in the same regional assessment and an international test. This makes adjusted test scores comparable over time, across subjects, across schooling levels, over countries and over all assessments.