* Defining "college": Do we count community colleges, four-year colleges, universities, trade schools? Different definitions will drastically alter the results.
* Defining "per capita": Using city limits vs. metropolitan area population will produce different rankings. College populations themselves can significantly skew per capita calculations for smaller cities.
* Data Collection: This kind of comprehensive data would require significant research compiling from various sources, and isn't routinely tracked in a standardized manner.
While some cities like Boston and New York City are known for their high density of higher education institutions, definitively declaring one as having the *most* per capita is not possible without a very detailed and arguably subjective study.