Jpcedotal actually makes a good point. There's a correlation between the decline of traditional religious beliefs* and the increase of superstition.
One study (
Determinants of Superstition) noted that while religiousity in general is more likely to increase belief in the supernatural, there was a negative correlation between church attendance and superstitious beliefs. In fact superstitious belief were actually most common in post-communist countries.
Other studies (Baylor
2005 and
2007) also noted a negative link between religious beliefs / church attendance and belief in creatures which don't exist and superstition. For example:
- When asked whether they believed Bigfoot existed, the highest percentage of people who though the "probably" or "absolutely" existed were those with no religion. Similarly, those who attended church less than one a year were also the most likely to believe they "absolutely" existed. [2007 survey]
- When asked it it was possible to comunicate with the dead, those who never attended church were the most likely to "strongly agree" it was possible. Those with no religion were also the most likely to "strongly agree" and the least likely to "disagree" (although it's worth pointing out they were also the most likely to "strongly disagree"). [2005 survey]
* I say "traditional" because protestant and liberal christians are significantly more likely to be superstitious than Catholic or conservative Christians.