Quantitative astrology

I've increasingly started to wonder how the degree of planetary influence is calculated. How can we compare the strength between planets? Magnetism, gravitational pull, distance, mass and other features... This could especially be a problem with these outer planets as their influence could be sinking into white noise of asteroid belt.

I wonder how to quantify the individual influence of heavenly bodies. This science was easy when astronomy was about geometry and omens. Astronomy developed through mathematics and physics, but astrology stayed behind. Nowadays when we do charts and readings, we basically rely on memorized information and lists of various relations between planetary positions and their effects on us.

Astrology seems to appear intertwined with different mythologies. Which came first? Probably astrology, maybe it was an object for cultural exporting. New target countries had their own versions of foreign spiritual science... Fascinating. Does anyone have information on development of astrology, instead of dogmatic following of various rule sets? Any recommended readings?