What is the effect of having the story broken into three parts?

Three is a predominant number throughout the novel. There are three parts, three countries (Oceania, Eastasia, and Eurasia), three classes of people (high, middle, and low), three slogans, and the oft repeated and revised "three year plan". I think the repetition is meant to engage the reader..... the reader is supposed to notice. Thus, it is a toll of the author and a part of the way the author writes.