SELECT MAX("Population") FROM table_12243 WHERE "Median family income" = '$53,946'
Which Population has a Median family income of $53,946?
CREATE TABLE table_12243 (
    "County" text,
    "Per capita income" text,
    "Median household income" text,
    "Median family income" text,
    "Population" real,
    "Number of households" real
)