Stacked bar charts · 5 marks

Answer the following questions based on the graph.

(i) In 2003, approximately how many total objects were found orbiting Earth in space? In what year did this number double?
(ii) Find the approximate number and share of payload objects and other objects in the year 2025.
(iii) What can you say about the number of payload objects over time, and the number of other objects over time? What can you say about the share of payload objects over time, and the share of other objects over time?

Answer: (i) About 10,000 objects in 2003; it doubled to about 20,000 in about 2021–2022. (ii) 2025: about 33,000 objects, roughly 16,500 payload (≈ 50%) and 16,500 other (≈ 50%). (iii) Payload objects grew slowly for decades, then shot up after about 2019; other objects grew steadily, with jumps in 2007 and 2009. The payload share stayed near 20–25% until about 2019 and rose to about 50% by 2025, so the share of other objects fell from about 75–80% to about 50%.

Step-by-step solution

Idea: The top of each column is the total. The lower (payload) piece is read from 0; the other objects are the total minus the payload piece. Share = parttotal × 100.

(i) In 2003, approximately how many total objects were found orbiting Earth in space? In what year did this number double?

The 2003 column reaches the 10,000 line: about 10,000 objects.1 mark
Double is about 20,000. The total reaches the 20,000 line in 2021, and 2022 is the first column clearly above it, so the number doubled in about 2021–2022.½ mark

About 10,000; doubled in about 2021–2022

(ii) Find the approximate number and share of payload objects and other objects in the year 2025.

2025 column: total ≈ 33,000; the payload piece reaches ≈ 16,500, so other objects ≈ 33,000 − 16,500 = 16,500.1 mark
Shares: payload ≈ 16,50033,000 × 100 ≈ 50%; other objects ≈ 50%.½ mark

Payload ≈ 16,500 (≈ 50%); other ≈ 16,500 (≈ 50%)

(iii) What can you say about the number of payload objects over time, and the number of other objects over time? What can you say about the share of payload objects over time, and the share of other objects over time?

Numbers: payload objects rose slowly (about 1,400 in 1990, 2,300 in 2003, 3,700 in 2019) and then very fast (about 16,500 by 2025), as thousands of small satellites were launched. Other objects (debris, rocket stages) grew steadily, with sudden jumps around 2007 and 2009 (break-ups creating debris), and grew more slowly in recent years. Both can only rise, since the chart is cumulative.1 mark
Shares: from the 1980s to about 2019 payload objects were only about a fifth to a quarter of the total (2003: 2,30010,000 ≈ 23%), and other objects about three-quarters or more. After 2019 the payload share rose quickly to about 50% in 2025, so the share of other objects fell to about 50%.1 mark

Payload: slow then very fast growth, share ≈ 20–25% → ≈ 50%. Other: steady growth with jumps, share ≈ 75–80% → ≈ 50%.

(i) About 10,000 in 2003, doubling to about 20,000 in about 2021–2022. (ii) In 2025, about 16,500 payload objects (about 50%) and about 16,500 other objects (about 50%) out of about 33,000. (iii) Payload objects grew slowly and then very rapidly after 2019; other objects grew steadily with jumps. The payload share was about 20–25% for decades and rose to about 50%; the share of other objects fell correspondingly.

Check: Shares in each year must add to 100%: in 2025, 50% + 50% ✓; in 2003, about 23% + 77% ✓. Readings are approximate; answers within a few hundred objects are fine.

Answer to write in the exam

(i)

Total in 2003 ≈ 10,000

Double ≈ 20,000, reached in 2021–2022

∴ About 10,000 objects; doubled by about 2021–2022

(ii)

Total (2025) ≈ 33,000; payload ≈ 16,500

Other ≈ 33,000 − 16,500 = 16,500

∴ Payload ≈ 50%, other objects ≈ 50%

(iii)

Payload: slow growth till ≈ 2019, then very fast (≈ 3,700 → ≈ 16,500)

Other objects: steady growth, jumps around 2007 and 2009

Payload share ≈ 20–25% (e.g. 2003: ≈ 23%) → ≈ 50% in 2025

∴ Share of other objects fell from ≈ 75–80% to ≈ 50%

Common mistakes that cost marks

Reading the top of the column as the number of other objects. Other objects = total − payload piece.
Saying the number of other objects fell after 2020. Their number still rose; only their share fell.
Taking the doubling year as 2007 because of the big jump that year; the total then is only about 13,000, not 20,000.

How this can come in the exam

Case-based (4 marks)

A city’s registered vehicles were: 2015, two-wheelers 60,000 and cars 20,000; 2025, two-wheelers 90,000 and cars 60,000.
(i) Find the total in each year. (ii) Find the share of cars in each year. (iii) Did the number of two-wheelers fall? Did their share fall? (iv) Which chart shows both the totals and the parts?

Show answer

(i) 80,000 and 150,000 (1 mark). (ii) 25% and 40% (1 mark). (iii) Number rose (60,000 → 90,000) but share fell (75% → 60%) (1 mark). (iv) A stacked bar (column) chart (1 mark).

Try one yourself

In a stacked column, a year’s total is 24,000 and the lower piece reaches 6,000. Find the other piece and both shares.