In 1984, what are the four ways an elite group falls from power?

In George Orwell's "1984" Winston and Julia have finally met with O'Brien and he has gotten them a copy of "The Book."  Winston begins to read out loud to Julia about the different classes and different levels.  Winston reads that there are four ways the ruling group can fall out of power.  One way is that they are beaten by another country or from without.  A second way they can lose power is that their ability to rule is inefficient and there is a revolt within the group itself.  A third way a group in power falls is that they let a strong Middle group develop and encroach on their power.  The fourth and final way to lose power is to lose their self-confidence or they lose the desire to rule. This is paraphrased from page 208 in my edition of "1984"