Via a FB friend:

As of April 1, 2006, out of a 2004 Census estimated population of 18 in Teterboro, there were 39 registered voters (216.7% of the population, vs. 55.4% in all of Bergen County).

Sadly, the answer may be prosaic. From earlier in the same Wikipedia entry:

The 2000 census failed to count any of the residents of the Vincent Place housing units who had moved into the newly built homes in 1999. The uncounted residents, including the Mayor and all four Council members, would help make up a projected tripling of the population enumerated by the census.