Final answer:
The question about the greatest proportion of tusked females cannot be answered without the proper dataset or graph showing these proportions over the specified years.
Step-by-step explanation:
The question provided does not include sufficient data to determine the greatest proportion of tusked females in a given population. If we assume the population in question relates to elephants, which are animals known for having tusks, there should be a graph or dataset that indicates the proportion of tusked females over the given years: 2005, 2010, 2015, and 2020. However, without specific data on the number of tusked females or the total population of females for those years, it is impossible to answer the question accurately.