Component comparison. In this form of comparison, you show the size of each part as a percentage of the total. For example, “Two-thirds of all mortgage loans were made within a fivecounty area.” Or, “Five sales representatives accounted for nearly 60 percent of all revenues during August.”

Item comparison. In an item comparison, you hope to show how things rank: are they about the same or is one more or less than the others? For example, “In January, the Northeast region exceeded the natural gas use of all other regions.” Or “During the second quarter of this fiscal year, Morgan Stanley ranked third among all investment banks in IPO activity.”

Time series comparison. In this comparison, we don't care about which part of the total an item might be, nor are you concerned with how they're ranked. You focus on how they change over time and whether the trend is increasing, decreasing, fluctuating or remaining constant. For example, “Airline seating capacity has declined sharply since the merger of 2015.” Or, “Interest rates 43 have risen slowly over the past twenty-four months.”

Frequency distribution comparison. A comparison of this type shows how many items are distributed into a series of progressive numerical ranges. For example, “More than 30 percent of U.S. adults earn between $36,000 and $48,000 per year.” Or, “Nearly 60 percent of adults 55 and older read a daily newspaper.”