However none of the criticisms have demonstrated a systematic bias in all the ratings. Most of the evidence consists of anecdotal evidence of relatively few cases. Whether there is a systematic or sporadic slant in Gastil's ratings is an open question" (Bollen, 1986, p. 586).[4] The freedom index of Freedom in the World has a very strong and positive (at least an 80%) correlation with three other democracy-indices studied in Mainwaring (2001, p. 53).[20]