The words IELTS actually tests

To increase suddenly and by a large amount.

Applications for computer science surged between 2016 and 2020.

Tip: Use it only for big, fast rises. For steady growth, say 'rose steadily'.

To fall very quickly and by a large amount.

Visitor numbers plummeted in 2020 before recovering the following year.

To rise and fall repeatedly.

Sales fluctuated between 40 and 55 units throughout the year.

Tip: Give the range it moved within: 'fluctuated between X and Y'.

To stay at the same level after a period of change.

After rising for a decade, the figure plateaued at around 30%.

To reach the highest point.

Electricity use peaked at 7 p.m., when most people were at home.

By a very small amount.

The proportion of cyclists rose marginally, from 4% to 5%.

By a large amount.

Spending on transport was considerably higher in 2020 than in 2010.

Gradually and at a regular rate.

The number of train passengers increased steadily over the period.

To form a particular part or proportion of something.

Clothing accounted for almost a third of online sales in 2022.

Tip: Ideal for pie charts: 'X accounted for 31% of the total'.

In the same order as the items just mentioned.

Car and bus use stood at 62% and 18% respectively.

Tip: It lets you give two figures in one sentence without repeating yourself.

To become greater than something that was previously greater.

Computer science overtook business as the most popular subject in 2018.

Considering everything; used to introduce the main trend.

Overall, three of the four museums attracted more visitors over the period.

Tip: Every Task 1 answer needs an overview. Starting it with 'Overall' makes it easy for the examiner to find.