|tag of unknown meaning and unclear purpose added by imports from official US sources|
|Used on these elements|
|Status: in use|
|Tools for this tag|
Meaning of that tag is unclear and it is dubious whatever it should be present on any object.
In http://www2.census.gov/geo/pdfs/maps-data/data/tiger/tgrshp2008/TGRSHP08.pdf it is defined as "Current urban area central place indicator" and restricted to be string of length 1.
In OSM database values tiger:CPI=Y and tiger:CPI=N clearly dominate what suggests that it may be boolean value. Though it is not clear whatever yes/no applies to "Current" part, "urban" part or some other segment of definition.