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Creating image alt text

See also:

General guidelines

  • All figures should have alt text, except standalone tables and ornamental figures.
    • Standalone tables are tables such as Figure 2.2c in The Economy 2.0: Microeconomics.
    • Ornamental figures are all pictures without number or caption which could be removed without any loss of information. For example, all the ‘Great Economist’ pictures (Adam Smith, Elinor Ostrom, and so forth) are ornamental pictures.
  • Alt text should allow the reader to understand the key message of the figure without having to refer to the text (readers should be able to get all the information they need from the alt text instead of searching the text for the complete explanation). A user should be able to use the figure outside the text without loss of information.
  • Alt text should simply be a written description of the diagram. It should not include any pedagogical content (for example, definitions of concepts or explanations of the underlying intuition). All pedagogical content should be in the main text or slideline captions.
  • Keep alt text as concise as possible while conveying the main points of the image. A rough guideline for description length is 20–50 words (1–3 sentences) for simple diagrams, and 50–200 words (3–8 sentences) for complex diagrams. These limits can be surpassed if the image is particularly complex to describe. Even so, alt text should be as concise as possible.
  • Use present tense.
  • When using initialisms or acronyms, state the full term first, for example, purchasing power parity (PPP), unless the term is easily identifiable (for example, GDP). Always capitalize initialisms and acronyms.
  • A good rule of thumb when thinking about what to include/not include is to imagine that you need to draw the figure from the description alone—what is the main point of the figure, and what information is crucial for understanding the figure?
  • The language used should be accessible for non-sighted readers. In particular:
    • Don’t use the words ‘left’ and ‘right’. For example, in composite graphs, rather label the panels and refer to ‘panel a’ and ‘panel b’, and for dual-axis graphs, you might use ‘the first vertical axis’ and the ‘second vertical axis’, along with their full labels.
    • The words ‘above’ and ‘below’ can be used if necessary (for example, ‘curve A is above curve B’).
    • Don’t use sight-related words for example, ‘you can see that …’ (use neutral synonyms such as ‘shows’ and ‘indicates’).
    • Don’t use words related to colour for example, ‘the green line’ or ‘the red shaded area’.
  • Don’t start with ‘picture of’ or ‘image of’ (or similar words). Do start with a statement of what the image is for example, a bar chart, a diagram, followed by a more detailed description. Use the most appropriate word from the following list:
    • Bar chart (or stacked bar chart)
    • Line chart
    • Scatterplot
    • Diagram (for anything that describes a model, including descriptions in words only)
    • Table (if it accompanies a chart)
    • Payoff matrix (use as a single phrase and not ‘matrix’ on its own)
    • Flowchart
  • Use the correct Unicode symbols for special characters like the minus sign. For example if you simply use a hyphen, many screen-readers read it aloud as ‘dash’ not ‘minus’.
  • Use words for large numbers (for example, ‘5 million’ rather than ‘5,000,000’).
  • When possible, use written descriptions of maths rather than LaTeX. Any LaTeX/MathJax included within alt text will appear in alt text in its plain text form. So MathJax delimiters ($$) aren’t needed and only clutter the alt text. Assistive-technology users will have to interpret your LaTeX syntax to understand the maths you intend. This should work fine for simple expressions like E = mc^2, but might make little sense for more complex expressions, for example, with fractions or multi-line braces. An option for including complex expressions in an accessible way is to rather make them part of the figure caption, as any maths included there will render in a manner that can be understood and relayed to users by assistive technology.
  • Write any superscripts and subscripts as normal lowercase text (as read-aloud functions do not pick up the difference).
  • We suggest that you use your computer’s or word processing software’s read-aloud function to check that the alt text reads in the intended way.

Guidelines for specific types of charts

1. Data chart (single)

Describe the key features in this order:

  1. State the variables on the horizontal axis first and then on the vertical axis, and their ranges.
    • Use the terminology ‘horizontal axis’ and ‘vertical axis’ and not ‘x-axis’, ‘y-axis’.
    • Use active tenses, for example, ‘The horizontal axis displays …’
    • If there are multiple variables on one axis, describe them as follows: ‘The [horizontal/vertical] axis shows two measures: [ ] and [ ].’ For example: ‘The horizontal axis shows two measures: output and hours of labour.’
  2. List the data series that appear in the chart, in the order they are listed in the legend.
  3. Describe the main takeaways from the figure (for example, general patterns, trends, relationships or comparisons between variables, outliers). Use the in-text description of the figure to determine what the main takeaways are.
Example 1

See The Economy 1.0’s Figure 1.10, and its alt text:

Alt text: In this line chart, the horizontal axis displays years from 1950 to 1989. The vertical axis displays GDP per capita in 1990 US dollars. It is in ratio scale (base 2) and ranges from 1,500 to 24,000 US dollars. GDP per capita for West Germany, Japan, Spain and East Germany are shown. GDP per capital increases over time for all countries. West and East Germany’s GDP increases at roughly the same rate, but West Germany’s GDP is at a higher level than East Germany’s. Japan’s and Spain’s GDP is below that of West and East Germany in 1950, but increases at a faster rate, so Japan and Spain’s GDP reaches the same level of East Germany’s GDP in the early 1960s, and approaches that of West Germany by 1989.

Example 2

See The Economy 1.0’s Figure 20.8, and its alt text:

Alt text: This stacked bar chart shows the amount of carbon dioxide (in trillions of tonnes) that would be emitted from burning different amounts and types of fossil fuels and the associated temperature increase relative to 1861–1880 (in degrees Celsius). One stacked bar refers to fossil fuel resources and indicates that burning all the oil resources corresponds to 1.8 trillion tonnes of carbon dioxide emissions and a temperature increase of 2 degrees Celsius, burning all the oil and gas resources corresponds to 3.3 trillion tonnes of carbon dioxide emissions and a temperature increase of 3 degrees Celsius, and burning all the oil, gas, and coal/lignite resources corresponds to 50 trillion tonnes of carbon dioxide emissions and a temperature increase of more than 5 degrees Celsius. Another stacked bar refers to fossil fuel reserves, and indicates that burning all the oil, gas, and part of the coal/lignite reserves corresponds to 1.8 trillion tonnes of carbon dioxide emissions and a temperature increase of 2 degrees Celsius, and burning all the oil, gas, and coal/lignite resources corresponds to 3.3 trillion tonnes of carbon dioxide emissions and a temperature increase of 3 degrees Celsius.

2. Diagram (single)

Describe the key features in this order:

  1. State the variables on the horizontal axis first and then on the vertical axis, and their ranges (if labelled on the axes).
    • Use the terminology ‘horizontal axis’ and ‘vertical axis’ and not ‘x-axis’, ‘y-axis’)
    • Use active tense, for example, ‘The horizontal axis displays …’
    • If there are multiple variables on one axis, describe them as follows: ‘The [horizontal/vertical] axis shows two measures: [ ] and [ ].’ For example: ‘The horizontal axis shows two measures: output and hours of labour. Coordinates are (measure on the horizontal axis, …).’
  2. State how many lines or curves there are in the diagram, and their labels. For each line or curve, clearly specify the features that are essential to understanding the figure (for example, shape, concavity, relative position in the diagram). Where relevant, provide coordinates of points on the line, or the equations of the line. For each line, evaluate whether it is more convenient to refer to it by using the label used on the diagram, or by paraphrasing its label.
  3. Describe the intersection points or points of tangency (if any).
  4. Describe specific regions of the graph that are shaded or labelled (if any).
    • In this instance, evaluate whether it would be more explicative to simply identify the region and its label, for example, ‘The region enclosed by points ABC is the deadweight loss’, or to briefly explain the intuition linked to the specific region highlighted, for example, the alt text used for the image in Section 9.5, Question 9.5 of The Economy 1.0 reads:

      In this diagram, the horizontal axis displays employment for the whole economy. The vertical axis displays two measures: average product of labour lambda, and real wage W-over-P. A vertical line at the end of the horizontal axis is the labour supply. A horizontal line represents the average product of labour lambda. Another, lower horizontal line is the price-setting curve, and corresponds to the price-setting real wage. A point, labelled A, lies at a relatively high level of employment, and between the average product of labour curve and the price-setting curve. At A, the real wage is too high and the markup too low; firms raise price; and given demand, output falls. A point, labelled B, lies on the price-setting curve at a level of employment lower than at A. A point, labelled C, lies at a level of employment and real wage lower than at B. At C, the real wage is too low and the markup too high; firms lower price; and given demand, output rises.

Example 1

See The Economy 1.0’s Figure 10.5, and its alt text:

Alt text: In this diagram, the horizontal axis shows consumption now, and the vertical axis shows consumption later. Coordinates are (consumption now, consumption later). Julia’s endowment is the point (0, 100), and Marco’s endowment is the point (100, 0). Two parallel, downward-sloping, convex curves are shown, representing the reservation indifference curves of Julia and Marco, and are labelled as Julia’s reservation indifference curve and Marco’s reservation indifference curve, respectively. Julia’s reservation indifference curve intersects the vertical axis at (0, 100). Marco’s reservation indifference curve lies above Julia’s and intersects the horizontal axis at (100, 0).

Example 2

See The Economy 1.0’s Figure 12.6, and its alt text:

Alt text: In this diagram, the horizontal axis shows the quantity of bananas, in tonnes per year, ranging from 0 to 100,000. The vertical axis shows costs in dollars, ranging from 0 to 900. The marginal social cost curve lies above the marginal private cost curve at every point. The horizontal price line at 400 dollars intersects the marginal social cost curve at a quantity of 38,000 (the point P2), which is the Pareto-efficient quantity, and intersects the marginal private cost curve at a quantity of 80,000 (the point A). The total compensation paid to produce the Pareto-efficient quantity is the area enclosed between the marginal social cost curve and marginal private cost curve, from the quantity of 0 to 38,000 tonnes.

3. Flowchart or infographic

Describe the key features in this order:

  1. Provide one sentence that states the purpose of the flowchart/infographic.
  2. Clearly specify the relationship between the concepts illustrated in the flowchart, using conceptual descriptions (such as ‘X leads to Y’) rather than literal descriptions (such as ‘there is an arrow from X to Y’).

Note: As much as possible, use the text exactly as it appears in the flowchart.

Example 1

See The Economy 1.0’s Figure 15.16, and its alt text:

Alt text: The flowchart shows the sequence of events following a fall in investment, using Australia as an example. A fall in investment leads to a fall in aggregate demand, which leads to a fall in forecast inflation. In response, Australia’s central bank cuts the interest rate, which leads to a fall in demand for Australian bonds, then a fall in demand for the Australian dollar, and then a depreciation of the Australian dollar. Exports then become relatively cheaper and imports more expensive, so net exports increase, resulting in an increase in aggregate demand.

Example 2

See The Economy 1.0’s Figure 16.21, and its alt text:

Alt text: The flowchart shows the relationships and variables that determine the unemployment rate and growth rate of real wages. The unemployment rate and growth rate of real wages depend on the price-setting curve (The Economy Units 9, 15, and 16) and the wage-setting curve (The Economy Units 6, 9, 15, and 16). The wage-setting curve is the result of conflict over work and wages (The Economy Unit 6), which affects the decisions of wage-setting by firms and work effort by workers (The Economy Units 6 and 9). The price-setting curve depends on productivity growth (The Economy Units 1, 2, and 3) that is driven by technological change (The Economy Units 1, 2, and 3), as well as job creation and destruction, and firm entry and exit (The Economy Unit 16), which in turn affects the Beveridge curve (The Economy Unit 16) and the wage-setting curve.

4. Payoff matrices

Describe the key features in this order:

  1. Specify the actors and the actions available to them.
  2. Specify the coordinate format for payoffs (if payoffs are given as numbers).
  3. Going from top left to bottom right, describe the actions taken by actors and their payoffs, for example: ‘If A does X and B does Y, their payoffs are (a, b)’.

Note: Avoid using the word ‘matrix’ or ‘table’ or orientation words such as ‘left’ or ‘right’; the alt text should only describe actors, actions, and payoffs.

Example 1

See The Economy 1.0’s Figure 4.1, and its alt text:

Alt text: This diagram shows Anil and Bala’s available actions, which are growing rice or growing cassava. If Anil and Bala grow rice, there is a glut of rice, which sells at a low price, and a shortage of cassava. Moreover, Anil is better able to produce cassava than rice. If Anil grows rice and Bala grows cassava, there is no market glut, and rice and cassava sell at high prices. However, Anil and Bala produce the crop for which they are less suited. If Anil grows cassava and Bala grows rice, there is no market glut, and rice and cassava sell at high prices. Moreover, Anil and Bala produce the crop for which they are better suited. If Anil and Bala grow cassava, there is a glut of cassava, which sells at a low price, and a shortage of rice. Moreover, Bala is better able to produce rice than cassava.

Example 2

See The Economy 1.0’s Figure 13.17, and its alt text:

Alt text: In this diagram, each firm can choose to invest, or not to invest. Outcomes are represented as coordinates where Firm A’s payoff is listed first, and Firm B’s payoff is listed second. If Firm A invests and Firm B invests, their payoffs are (100, 100). If Firm A invests and Firm B does not invest, their payoffs are (−40, 80). If Firm A does not invest and Firm B invests, their payoffs are (80, −40). If Firm A does not invest and Firm B does not invest, their payoffs are (10, 10).

5. Multiple data or diagrams in the same figure

The same guidelines above apply to individual chart or diagram descriptions, with the following additional guidelines:

  1. State how many charts or diagrams are in the figure.
  2. Describe each chart or diagram according to the guidelines for individual charts or diagrams, going from the top-left to the bottom-right chart or diagram, where possible.

Note: Charts or diagrams should be referred to as Diagram 1 (or Chart 1), Diagram 2 (or Chart 2), and so on. The numbering should be assigned from top-left to bottom-right.

Example 1

See The Economy 1.0’s Figure 11.18, and its alt text:

Alt text: There are two diagrams. In diagram 1, the horizontal axis shows quantity and the vertical axis shows price. Coordinates are (quantity, price). There are two parallel, downward-sloping, straight lines. The upper line is labelled Demand1 and the lower line is labelled Demand0. There is one upward-sloping, straight line labelled Supply, which intersects Demand0 at the point (Q0, P0) and intersects Demand1 at the price P1.

In diagram 2, the horizontal axis shows price in period t and the vertical axis shows price in period t+1 on the vertical axis. Coordinates are (price in period t, price in period t+1). A 45-degree line indicates where the price is unchanged from year to year. An upward-sloping, steeper, straight line shows the price dynamics curve, denoted PDC, and intersects the 45-degree line at the point (P0, P0). A series of vertical arrows departing from the 45-degree line and horizontal arrows departing from the price dynamics curve line connect the two lines. These arrows show that prices keep increasing in each period once they depart the equilibrium point (P0, P0).

Example 2

See The Economy 1.0’s Figure 20.23, and its alt text:

Alt text: There are three diagrams. Diagram 1 shows the feedback loop associated with extensive summer sea ice. If there is extensive summer sea ice, solar radiation is reflected rather than absorbed, leading to lower temperatures, which in turn maintain the extensive summer sea ice. Diagram 2 shows the feedback loop associated with no summer sea ice. If there is no summer sea ice, solar radiation is absorbed rather than reflected, leading to higher temperatures, which in turn make it impossible for summer sea ice to form. In diagram 3, the horizontal axis shows sea ice in period t and the vertical axis shows sea ice in period t+1. There are two curves. The 45-degree line shows the line of unchanging environment, where sea ice coverage is the same in this period and next period. The environmental dynamics curve, denoted EDC, is S-shaped and intersects the 45-degree line at three points, listed in order of the amount of sea ice in period t: point C is a low stable equilibrium (no summer sea ice), point A is an unstable equilibrium (tipping point) of medium sea ice levels, and point B is a high stable equilibrium (extensive summer sea ice). If the amount of sea ice is exactly that shown at point A, it will not change with time. If the amount of sea ice is between the amounts shown by points A and B, it will increase with time until the amount shown by point B. If the amount of sea ice is between the amounts shown by points A and C, it will decrease with time until the amount shown by point C.

6. Slideline figures

The same guidelines above apply to descriptions of individual slideline figures, with the following additional guidelines:

  • Just as the slideline figures ‘build on’ previous figures in the same slideline, the alt text for any slideline figure should ‘build on’ the alt text from previous figures in the same slideline.
  • The alt text should be written to be ‘standalone’, meaning that if we removed the figure from the slideline and readers only had the alt text, they should be able to understand the figure.
Example 1

See The Economy 1.0’s Figure 9.9 slideline, and alt text for each of the two figures it includes:

Slide 1 alt text: In this diagram, the horizontal axis shows two measures: units of output and hours of labour, and the vertical axis shows price in dollars. Coordinates are (measure of the horizontal axis, price). A downward-sloping straight line is labelled demand curve (given economy-wide demand). A horizontal line at a price of is labelled wage. Above the wage line, a horizontal line at a price of p-star crosses the demand curve at point B with coordinates (q-star, p-star). There are three parallel isoprofit curves, which are downward sloping, and convex. The uppermost curve is tangent to the demand curve at point B. The middle curve crosses the demand curve at point C, at a higher price and lower output than point B, and A, at a lower price and higher output than point B.

Slide 2 alt text: In this diagram, the horizontal axis shows two measures: units of output and hours of labour, and the vertical axis shows price in dollars. Coordinates are (measure of the horizontal axis, price). Coordinates are (output or hours, price). A downward-sloping straight line is labelled demand curve (given economy-wide demand). A horizontal line at a price of w is labelled wage. Above the wage line, a horizontal line at a price of p-star crosses the demand curve at point B with coordinates (q-star, p-star). There are three parallel isoprofit curves, which are downward sloping, and convex. The uppermost curve is tangent to the demand curve at point B. The middle curve crosses the demand curve at point C, at a higher price and lower output than point B, and A, at a lower price and higher output than point B. At an output of q-star, the distance between point B and the wage is the profit per unit of output. The distance between the wage and the horizontal axis is the wage per unit of output.

Example 2

See The Economy 1.0’s Figure 19.25 slideline, and alt text for each of the three figures it includes:

Slide 1 alt text: In this diagram, the horizontal axis shows the cumulative share of the world’s income recipients (as a percentage) and the vertical axis shows the cumulative share of income (as a percentage). Ordered from poorest to richest, 20% of the world’s population are Chinese rural workers, 50% are Chinese urban workers, 25% are European and North American workers, and 5% are owners of capital. The Lorenz curve connects the points (0, 0), (20, 0), (70, 20), (95, 70), and (100, 100). The area enclosed by the Lorenz curve and the 45-degree line from (0, 0) to (100, 100) indicates the initial level of inequality, corresponding to a Gini coefficient of 0.59.

Slide 2 alt text: In this diagram, the horizontal axis shows the cumulative share of the world’s income recipients (as a percentage) and the vertical axis shows the cumulative share of income (as a percentage). Ordered from poorest to richest, 10% of the world’s population are Chinese rural workers, 60% are Chinese urban workers, 25% are European and North American workers, and 5% are owners of capital. The Lorenz curve connects the points (0, 0), (10, 0), (70, 30), (95, 60), and (100, 100). Initially, 20% of the world’s population are Chinese rural workers and 50% are Chinese urban workers, and the Lorenz curve connected the points (0, 0), (20, 0), (70, 20), (95, 70), and (100, 100). Compared to the initial situation, income has been redistributed from European and North American workers to Chinese workers and owners of capital, causing the Gini coefficient to decrease.

Slide 3 alt text: In this diagram, the horizontal axis shows the cumulative share of the world’s income recipients (as a percentage) and the vertical axis shows the cumulative share of income (as a percentage). Ordered from poorest to richest, 10% of the world’s population are Chinese rural workers, 60% are Chinese urban workers, 25% are European and North American workers, and 5% are owners of capital. The Lorenz curve connects the points (0, 0), (10, 0), (70, 30), (95, 60), and (100, 100). Initially, 20% of the world’s population are Chinese rural workers and 50% are Chinese urban workers, and the Lorenz curve connected the points (0, 0), (20, 0), (70, 20), (95, 70), and (100, 100). Compared to the initial situation, income has been redistributed from European and North American workers to Chinese workers and owners of capital. The Gini coefficient decreases from 0.59 to 0.545.

7. Figures that are part of an exercise or MCQ

The same guidelines above apply to these figures, with the following additional guidelines:

  • Describe all elements of the figure that are needed to answer the exercise or MCQ, in the appropriate level of detail (for example, do readers need to know the exact equation of a line or just that it is upward-sloping and intersects another line at point X?)
  • Keep descriptions as literal as possible (for example, ‘the payoff is 4’), and be careful not to add interpretations or give hints to the solution (for example, ‘there is one Nash equilibrium’).
Example 1

See The Economy 1.0’s Question 9.5 figure, and its alt text:

Alt text: In this diagram, the horizontal axis shows employment in the whole economy and the vertical axis shows the average product of labour and the real wage. There are two horizontal lines. The upper line is labelled average product of labour, denoted lambda. The lower line is the price-setting curve and shows the real wage, denoted Wps. Point B is on the price-setting curve. Point A is between the average product of labour and the price-setting curve, indicating a higher wage and level of employment. Point C is between the price-setting curve and the horizontal axis, indicating a lower wage and level of employment. If the wage is above the average product of labour, the real wage is too high and the markup is too low. Firms raise their price, and given demand, output falls. If the wage is below the price-setting curve, the real wage is too low and the markup is too high. Firms lower their price, and given demand, output rises.

Example 2

See The Economy 1.0’s Question 12.2 figure, and its alt text:

Alt text: In this diagram, the horizontal axis shows output, denoted Q, and the vertical axis shows cost in dollars. The marginal social cost curve, denoted MSC, lies above the marginal private cost curve, denoted MPC. Both curves start at the point (0, 100) and are upward-sloping lines. The price curve is horizontal at 340 dollars. At Q = 80, the marginal private cost is 260 dollars, and the marginal social cost is 340 dollars. At Q = 120, the marginal private cost is 340 dollars, and the marginal social cost is 460 dollars.

Note: To answer the question, readers need to know the intersection of the MSC and MPC with the price curve at Q = 80, and the vertical-axis values of the MSC and MPC at Q = 120.