This kind of essay calls for statistics, proportions, and percentages as the "engine" for the essayist's point of view. Given the time necessary to gather those statistics, a good thesis statement would sound something like this: "I believe that X is true based on the following gathered information: Y." The type of information informs the thesis statement. Some examples might serve to clarify this approach. Example A: "From counting the number of goldfinches on my bird feeder, and observing how many have turned spring yellow from their winter brown color in consecutive months, I have determined that this spring season has arrived later than spring arrived in previous years." This quantitative research project would, by definition, take several years. Example B: "From counting the number of flip-flops at the mall this afternoon, I have determined that more women than men wear flip-flops." This research project would only take one afternoon, and would be less "scientific" because of the small sample of quantitative information. Example C: Observing via MapQuest the locations of several franchise restaurants in four cities, I have determined that fast-food restaurants (McDonald's, Taco Bell, etc.) cluster around auto-orientated locations (freeway exits, strip malls, etc.) while dinner restaurants cluster around entertainment centers (theaters, concert halls, etc.). Your topic, then, will be largely dependent on the time and mobility available to the researcher. Another factor will be the area of inquiry: social, political, scientific, etc.