The poverty of the peasants was certainly a contributing factor in the revolution of 1789. However, the privileges afforded to the nobility and clergy were the determining factors that ultimately led to the rise of revolutionary zeal. Despite the reforms of Necker, Colonne and Brienne, the first and second estate refused to budge on the issue of taxation. France's economic state worsened to a point almost beyond repair and revolution was inevitable.
Prior to 1789 France was ruled under the Ancien Regime social system, ancien regime means "old order". At this time Louis XIV was in power. He ruled an Absolute Monarchy. This meant that only the king ruled the country and the first and second estate had no say. France was ruled this way from 1643 - 1715.
Frances social system was divided into three estates. The king of course was considered closest to god and beneath him was the clergy otherwise known as the first estate. The Roman Catholic Church had many privileges, for example they did not have to pay taxes. In addition, they lived handsomely off the taxes paid by the third estate. The only people in the church who did not live well were the parish priests. This is because the parish priests had made a vow to live in absolute poverty.
The second estate was made up of the nobility. The nobles like the clergy owned land and did not have to pay taxes. The peasants worked for the nobles by working on their land providing produce. Most of the produce would be given to the nobility instead of paying money.
The peasants and the bourgeoisie made up the third estate and also ninety percent of the population. They are the people who "supported" the social structure by paying taxes. The third estate was the only estate that paid eighty-five percent of their pay in tax. In addition, one-tenth of their earnings also went to the church. They were taxed on almost everything from salt to crossing a road. Soon the tax expectations became so bad that the bourgeoisie who were educated started to take action demanding a reform.