Non-localized unit metadata includes unit conversions and unit preferences. This data is found in common/supplemental/units.xml.
All simple units known to CLDR (units without a dimensionality or SI prefix) should have a <convertUnit/> entry.
The following three guidelines are used to determine whether a proposed unit preference should be added to units.xml:
Usage needs to be reasonably broad
Country category to be captured needs to be major countries
Additional usage has to contrast with the default