The low agreement may be accounted for by the degree to which each astrologer adjusts for changes in planetary alignments (or whatever) since astrology was first established as a discipline. In other words, birth month for a particular astrological sign is different now than it would have been 2000 years ago.
Modern Astrology was established by Ptolemy who standardized on the Tropical Zodiac in the 2nd Century AD. In that system, the Sun always moves from Pisces to Aires on the Vernal Equinox. This was a more precise definition of what the ancient Babylonians did (defining the Zodiac based on 30 degree divisions of the Ecliptic).
I'm not arguing that Astrology is scientific, but I am saying it's precise, to the limits of the measurement technology of the time period in which it was defined.
