Which visualization method is used to show parts of a whole as percentages?

A pie chart is the most effective visualization method for displaying parts of a whole as percentages. Each slice of the pie represents a category's proportion relative to the entire dataset, making it easy to visualize how different segments compare to one another in terms of size. This method is particularly useful for showing the distribution of categorical data, allowing viewers to quickly grasp the relative sizes of each category.

In contrast, a histogram displays the frequency distribution of numerical data, which helps to understand the underlying frequency of data points within specified intervals, but does not express parts of a whole. A line graph is used to illustrate trends over time by connecting data points with a continuous line, thus focusing more on relationships between variables rather than proportions. A box plot summarizes the distribution of a dataset through its quartiles and highlights outliers, but it also does not represent parts of a whole as percentages.