An interactive study · 1778-2023
A longer life.
An unequal world.
Compare life expectancy across countries and years. The design critique explains the change from a 30-country bar chart to this interactive world map.
Life expectancy ranges from 54.5 to 86.4 years
2023 · hover or tap for values
The colour scale stays fixed across years. Modern geographic boundaries are used throughout; historical borders are not represented. Small territories may be absent from this simplified map; use the country selector to find them.
All selected countries gained years of life expectancy
Life expectancy at birth, years. Use the line patterns and end labels to follow each country.
Lines connect consecutive annual observations only. Gaps mean missing years. Each series has its own line pattern, and the vertical guide marks the selected year.
Original chart / critique / interactive redesign
From a country list
to a world map.
I first used a bar chart to compare life expectancy in 30 countries in 2023. For the redesign, I wanted readers to explore where life expectancy differs and then inspect a country's value.
01 / Original chart
The first version is a vertical bar chart of 30 selected countries in 2023. Its zero origin makes bar lengths proportional to the values.
Baseline chart created for this exercise from published data.
02 / Critique and response
| Design issue | Critique of the bar chart | What I changed |
|---|---|---|
| Crowded country names | Thirty names had to fit below the bars. I rotated them, which made the names harder to read. | I added an alphabetical country selector and a country profile with horizontal text. Readers can also click a place on the map. |
| Reading the values | The bars had no number labels, so readers had to estimate values from the grid. | The map shows a value on hover or tap. The country profile and comparison table show values rounded to one decimal place. |
| Seeing places | The list of country names did not show where the countries were. I wanted the new view to show geographic patterns. | I used a world map and a fixed light-to-dark colour scale. The original 30 countries keep the same 2023 values; the map also includes other countries and years. |
| World context | The first chart did not show the world estimate. Readers could compare countries, but had no worldwide reference. | I added the difference from the world estimate to the country profile. The supporting line chart includes the world series. |
What worked in the original
The original bar chart used a zero origin, one colour and clear labels for the year and unit. It remains useful for comparing the 30 countries at once. I kept the source values and clear units in the map.
03 / Redesigned visual: interactive world map
I used D3.js to build the interactive world map. Colour shows broad differences across places. Readers can select a country to see its value, compare it with the world estimate or explore another year.
Map colours are less precise than bar lengths, and large countries take up more space. The selector includes small territories. The comparison table shows up to five selected countries plus the world, ordered by value.
The year slider and supporting line chart add a way to explore change over time. This extends the original one-year comparison.
Design choices from the course guides
I used horizontal text, a clear title and direct values. The tables use left-aligned names and right-aligned numbers. The line chart uses different line patterns as well as colour, so it is easier to follow in black and white.
References: Summary at a Glance: Table Design; Summary at a Glance: Graph Design; Stephanie Evergreen and Ann K. Emery, Data Visualization Checklist (May 2016).
The PDF contains the original chart, critique and a static view of the redesigned map. Download the report.
Data and calculations
Source: Riley (2005); Zijdeman et al. (2015); HMD (2025); UN WPP (2024), with major processing by Our World in Data. This local snapshot was downloaded on 2 October 2026 and ends in 2023. For country data before 1950, sources are HMD and Zijdeman et al.; 1950 onward uses UN WPP.
Values retain source precision internally and are displayed to one decimal place. Change = selected-year value minus baseline-year value, in years, not percent. The selected country and world must both have an observation for a comparison. No forward filling, backward filling or interpolation is used. The map uses modern boundaries from Natural Earth via world-atlas 2.0.2.
Historical data coverage and source quality vary. Unusual annual drops can also reflect source methods: OWID notes that UN treatment of crisis deaths creates isolated dips for the Central African Republic in 2009 and 2022. The display preserves the published values; it does not independently validate those estimates.
Interaction guide and accessibility
Drag the year slider or use its arrow keys. Click a country on the map or use the alphabetical selector. Open "Compare countries" to add or remove series and choose a starting year. Hover or tap the trend chart to inspect a year. The table shows values rounded to one decimal place without requiring hover. "Play" advances through years and can be paused at any time.
Country names and values accompany colour. Each line has its own pattern; the selected-country marker has an outline. Keyboard focus is visible, all controls have labels, and the layout stacks on smaller screens. Downloaded year data contains all included countries and territories plus the world, including explicit blanks for missing observations.
About this exercise
Baseline chart created for this exercise from published data. The redesign is the interactive world map, with a country profile and supporting comparisons. The original 30 country values remain unchanged; the map includes more countries and a longer history.