permno-
date-
excode -
sic - letter "Z", value 711 (most are 4 digits),
ncusip -
ticker -
name -
naics -
primex -
permco -
cusip -
Price - Null values, negative numbers,
vol - null values
ret - null values, letter "B" as value multiple times, letter "C",
shout - null values
trade - null values
eqret -
vret -