I dont think authority has an effect on squalor. If I am correct authority determines how likely your generals will rebel, but rebellions are so rare, that I think authority is a junk stat.

I think you mean to say chivalry when you said authority. Chivalry in a governor increases growth and happiness. Dread does not increase growth, but does increase order.

My strategy for the economy is to put taxes on low, until the city grows to a huge city level. In the meantime I buy farms first, then ports, roads, markets, and happiness buildings. Setting taxes on low gives a growth bonus, and increases chivalry, which gives even faster growth.