The wide spread belief in astrology is probably based on the Forer Effect. In 1948 Bertram F. Forer, a psychology professor, gave his students a personality profile test. The next day he handed out personality descriptions to his students and asked them if they were apt. The average score for the profiles 'accuracy' was 4.26 out of a possible 5 (perfect personality description). However, every student had been given the same analysis which consisted of statements from various horoscopes columns in the media.
"You have a great need for other people to like and admire you. You have a tendency to be critical of yourself. You have a great deal of unused capacity which you have not turned to your advantage. While you have some personality weaknesses, you are generally able to compensate for them. Disciplined and self-controlled outside, you tend to be worrisome and insecure inside. At times you have serious doubts as to whether you have made the right decision or done the right thing. You prefer a certain amount of change and variety and become dissatisfied when hemmed in by restrictions and limitations. You pride yourself as an independent thinker and do not accept others' statements without satisfactory proof. You have found it unwise to be too frank in revealing yourself to others. At times you are extroverted, affable, sociable, while at other times you are introverted, wary, reserved. Some of your aspirations tend to be pretty unrealistic. Security is one of your major goals in life."
This experiment has been repeated many times with similar results. People like general & mostly positive statements about them made by "authority" figures and that "affirm" their uniqueness.