Lesson 8 of 22
Comparing static data and proportions
Static data presents a snapshot. Describe relative sizes and differences without inventing a time trend.
Incorrect for one-year data: “Cycling increased to 30% in Town A.”
Accurate: “Cycling accounted for 30% of journeys in Town A.”
Comparison patterns
| Pattern | Example |
|---|---|
| higher/lower than | The rate in A was higher than that in B. |
| the highest/lowest | C recorded the lowest proportion. |
| twice as high as | A's rate was twice as high as B's. |
| three times as many | A had three times as many visitors as B. |
| compared with | The share was 35%, compared with 20% in B. |
| whereas/while | A recorded 35%, whereas B stood at 20%. |
| account for | Housing accounted for 40% of expenditure. |
| exceed by | A exceeded B by 15 percentage points. |
Compare like with like: a town's percentage with another percentage, or its visitor number with another visitor number. “A's rate was higher than B” is less precise than “A's rate was higher than B's.”
Fractions, shares, and majorities
Around 25% is approximately a quarter; about 33% is roughly a third. A majority means more than half. A category with 45% may be the largest category without being a majority.
For countable things, use “number,” “many,” and “fewer”: the number of students, many cars, fewer visitors. For uncountable quantities, use “amount,” “much,” and “less”: the amount of water, much energy, less pollution.
Changes in a share do not always show changes in a total
If a household's food share falls from 30% to 20%, you know food accounts for a smaller proportion of its expenditure. You do not know whether the amount spent on food fell unless total spending is also supplied.
This distinction is especially useful for pie charts. Describe the information the proportions establish, rather than assuming that a smaller slice means fewer people, fewer products, or less money in absolute terms.