"Comparison between circles of different size should be absolutely avoided. It is inexcusable when we have available simple methods of charting so good and so convenient from every point of view as the horizontal bar." (Willard C Brinton, "Graphic Methods for Presenting Facts", 1919)
"In general, the comparison of two circles of different size should be strictly avoided. Many excellent works on statistics approve the comparison of circles of different size, and state that the circles should always be drawn to represent the facts on an area basis rather than on a diameter basis. The rule, however, is not always followed and the reader has no way of telling whether the circles compared have been drawn on a diameter basis or on an area basis, unless the actual figures for the data are given so that the dimensions may be verified." (Willard C Brinton, "Graphic Methods for Presenting Facts", 1919)
"Although the pie or sector chart ranks very high in popular appeal, it is held in rather low esteem by many specialists in graphic presentation. Since the pie chart possesses more weaknesses perhaps than most graphic forms, it is especially important to observe proper discretion in its construction and application. The pie chart is used to portray component relations. The various sectors of a circle represent component parts of an aggregate or total." (Calvin F Schmid, "Handbook of Graphic Presentation", 1954)
"First, it is generally inadvisable to attempt to portray a series of more than four or five categories by means of pie charts. If, for example, there are six, eight, or more categories, it may be very confusing to differentiate the relative values portrayed, especially if several small sectors are of approximately the same size. Second, the pie chart may lose its effectiveness if an attempt is made to compare the component values of several circles, as might be found in a temporal or geographical series. In such case the one-hundred percent bar or column chart is more appropriate. Third, although the proportionate values portrayed in a pie chart are measured as distances along arcs about the circle, actually there is a tendency to estimate values in terms of areas of sectors or by the size of subtended angles at the center of the circle." (Calvin F Schmid, "Handbook of Graphic Presentation", 1954)
"Circles of different size, however cannot properly be used to compare the size of different totals. This is because the reader does not know whether to compare the diameters or the areas (which vary as the squares of the diameters), and is likely to misjudge the comparison in either ease. Usually the circles are drawn so that their diameters are in correct proportion to each other; but then the area comparison is exaggerated. Component bars should be used to show totals of different size since their one dimension lengths can be easily judged not only for the totals themselves but for the component parts as well. Circles, therefore, can show proportions properly by variations in angles of sectors but not by variations in diameters." (Anna C Rogers, "Graphic Charts Handbook", 1961)
"Pie charts have weaknesses and dangers inherent in their design and application. First, it is generally inadvisable to attempt to portray more than four or five categories in a circle chart, especially if several small sectors are of approximately the same size. It may be very confusing to differentiate the relative values. Secondly, the pie chart loses effectiveness if an effort is made to compare the component values of several circles, as might occur in a temporal or geographical series. [...] Thirdly, although values are measured by distances along the arc of the circle, there is a tendency to estimate values in terms of areas by size of angle. The 100-percent bar chart is often preferable to the circle chart's angle and area comparison as it is easier to divide into parts, more convenient to use, has sections that may be shaded for contrast with grouping possible by bracketing, and has an easily readable percentage scale outside the bars." (Anna C Rogers, "Graphic Charts Handbook", 1961)
"Data should not be forced into an uncomfortable or improper mold. For example, data that is appropriate for line graphs is not usually appropriate for circle charts and in any case not without some arithmetic transformation. Only graphs that are designed to fit the data can be used profitably." (Cecil H Meyers, "Handbook of Basic Graphs: A modern approach", 1970)
"The varieties of circle charts are necessarily limited by the lack of basic design variation - a circle is a circle! Also, a circle can be considered as representing only one unit of area. regardless of its size. Thus, circle charts have limited applications, i.e., to show how a given quantity (area) is divided among its component parts,' or to show changes in the variable by showing area changes. A circle chart almost always presents some form of a part-to-total relationship." (Cecil H Meyers, "Handbook of Basic Graphs: A modern approach", 1970)
"While circle charts are not likely to present especially new or creative ideas, they do help the user to visualize relationships. The relationships depicted by circle charts do not tend to be very complex, in contrast to those of some line graphs. Normally, the circle chart is used to portray a common type of relationship (namely. part-to-total) in an attractive manner and to expedite the message transfer from designer to user." (Cecil H Meyers, "Handbook of Basic Graphs: A modern approach", 1970)
"A pie graph is a circle that is divided into wedges, like slices of a pie. It is particularly useful when statistics show as a half or a quarter of a total. The human eye can recognize half of a circle much more easily than half a length of a bar." (Dyno Lowenstein, "Graphs", 1976)
"Pie charts are awkward to label and do not fit as well on a report page as bar comparisons (vertical or horizontal). Thus a series of pies is less effective than a series of subdivided bars (or columns) for comparing a group of subdivided totals. Several pies require much more space than several bars. Moreover, the comparable components often are in a different location in each pie and so are hard to compare." (Peter H Selby, "Interpreting Graphs and Tables", 1976)
"The circle graph, or pie chart, appears to simple and 'nonstatistical', so it is a popular form of presentation for general readers. However, since the eye can compare linear distances more easily and accurately than angles or areas, the component parts of a total usually can be shown more effectively in a chart using linear measurement." (Peter H Selby, "Interpreting Graphs and Tables", 1976)
"A pie chart is comprised of a circle that is divided into segments by straight lines within the circle. The circle represents the total or whole amount. Each segment or wedge of the circle represents the proportion that a particular factor is of the total or whole amount. Thus, a pie chart in its entirety always represents whole amounts of either 100% or a total absolute number, such as 100 cents or 5,000 people. All of the segments of the pie when taken together (that is, in the aggregate) must add up to the total." (Robert Lefferts, "Elements of Graphics: How to prepare charts and graphs for effective reports", 1981)
"If you want to dramatize comparisons in relation to the whole. use a pie chart. If you want to add coherence to the narrative, the pie chart also helps because it depicts a whole. If your main interest is in stressing the relationship of one factor to another, use bar charts. If you wish to achieve all these effects. you can use either type of chart. and decide on the basis of which one is more aesthetically or pictorially interesting." (Robert Lefferts, "Elements of Graphics: How to prepare charts and graphs for effective reports", 1981)
"[…] the only worse design than a pie chart is several of them, for then the viewer is asked to compare quantities located in spatial disarray both within and between pies. […] Given their low data-density and failure to order numbers along a visual dimension, pie charts should never be used." (Edward R Tufte, "The Visual Display of Quantitative Information", 1983)
"Pie charts have severe perceptual problems. Experiments in graphical perception have shown that compared with dot charts, they convey information far less reliably. But if you want to display some data, and perceiving the information is not so important, then a pie chart is fine." (Richard Becker & William S Cleveland," S-Plus Trellis Graphics User's Manual", 1996)
"The most ubiquitous graph is the pie chart. It is a staple of the business world. [...] Never use a pie chart. Present a simple list of percentages, or whatever constitutes the divisions of the pie chart." (Gerald van Belle, "Statistical Rules of Thumb", 2002)
"This pie chart violates several of the rules suggested by the question posed in the introduction. First, immediacy: the reader has to turn to the legend to find out what the areas represent; and the lack of color makes it very difficult to determine which area belongs to what code. Second, the underlying structure of the data is completely ignored. Third, a tremendous amount of ink is used to display eight simple numbers." (Gerald van Belle, "Statistical Rules of Thumb", 2002)
"We make angle judgments when we read a pie chart, but we don't judge angles very well. These judgments are biased; we underestimate acute angles (angles less than 90°) and overestimate obtuse angles (angles greater than 90°). Also, angles with horizontal bisectors (when the line dividing the angle in two is horizontal) appear larger than angles with vertical bisectors." (Naomi B Robbins, "Creating More effective Graphs", 2005)
"But here’s the contradictory thing about pie charts. A common argument in favor of pie charts is that reading the labels compensates for what really are our difficulties in reading them accurately. […] this is not an argument in favor of pie charts; rather, it’s an argument to the detriment of visualization. Shouldn’t we be able to read the chart without deciphering all the labels? If we have to read both the labels and the chart, the chart becomes pointless, as labels should complement rather than entirely support it." (Jorge Camões, "Data at Work: Best practices for creating effective charts and information graphics in Microsoft Excel", 2016)
"The donut, its spelling betrays its origins, is nearly always more deceit friendly than the pie, despite being modelled on a life-saving ring. This is because the hole destroys the second most important value- defining element, by hiding the slice angles in the middle." (Nicholas Strange, "Smoke and Mirrors: How to bend facts and figures to your advantage", 2007)
"There are some chart types that occasionally appear in print but are so bad that they serve neither honesty nor deceit. Among these monuments to human ingenuity at the expense of common sense are the concentric donut and overlapping segments. The concentric donut is really just a bar or column chart bent back on itself to save space. However as anyone who has ever watched a two or four hundred metre race will know, to make sense of the order of arrival at the tape you have to stagger the start to take account of the bend in the track. Blithely ignoring this problem, the concentric donut uses to diminish the difference between the inner and the outer absolute values by anything up to 2.5 times." (Nicholas Strange, "Smoke and Mirrors: How to bend facts and figures to your advantage", 2007)
"[…] a graph is nothing but a visual metaphor. To be truthful, it must correspond closely to the phenomena it depicts: longer bars or bigger pie slices must correspond to more, a rising line must correspond to an increasing amount. If a graphical depiction of data does not faithfully follow this principle, it is almost sure to be misleading. But the metaphoric attachment of a graphic goes farther than this. The character of the depiction ism a necessary and sufficient condition for the character of the data. When the data change, so too must their depiction; but when the depiction changes very little, we assume that the data, likewise, are relatively unchanging. If this convention is not followed, we are usually misled." (Howard Wainer, "Graphic Discovery: A trout in the milk and other visuals" 2nd, 2008)
"Generally pie charts are to be avoided, as they can be difficult to interpret particularly when the number of categories is greater than five. Small proportions can be very hard to discern […] In addition, unless the percentages in each of the individual categories are given as numbers it can be much more difficult to estimate them from a pie chart than from a bar chart […]." (Jenny Freeman et al, "How to Display Data", 2008)
"Dealing with a circular visualization and trying to compare its radial portions is always problematic. When designing with data, the story should always be told as clearly as possible. To do so, it is often best to avoid round charts and graphs." (Brian Suda, "A Practical Guide to Designing with Data", 2010)
"Sometimes itʼs better to have fewer choices and focus on the charts that best convey the story. A doughnut chart is not one of these. By removing the centre of a pie chart, it further hinders the ability to judge the weight of each segment. Moving from a healthy wedge to two arcs makes it harder for people to comprehend what value is represented. We know that a full pie chart is one hundred per cent and that any wedge is a fraction of that; if we are presented with only an arc, is it equivalent to the wedge, or is it less because it is missing a portion?" (Brian Suda, "A Practical Guide to Designing with Data", 2010)
"Pie charts can be used effectively to summarize a single categorical data set if there are not too many different categories. However, pie charts are not usually the best tool if the goal is to compare groups on the basis of a categorical variable." (Roxy Peck et al, "Introduction to Statistics and Data Analysis" 4th Ed., 2012)
"The unique thing you get with a pie chart is the concept of there being a whole and, thus, parts of a whole. But if the visual is difficult to read, is it worth it?" (Cole N Knaflic, "Storytelling with Data: A Data Visualization Guide for Business Professionals", 2015)
"When it comes to presenting categorical data, pie charts allow an impression of the size of each category relative to the whole pie, but are often visually confusing, especially if they attempt to show too many categories in the same chart, or use a three-dimensional representation that distorts areas. [...] Multiple pie charts are generally not a good idea, as comparisons are hampered by the difficulty in assessing the relative sizes of areas of different shapes. Comparisons are better based on height or length alone in a bar chart." (David Spiegelhalter, "The Art of Statistics: Learning from Data", 2019)
"A great visual metaphor for representing structure is the pie chart. We divide it into slices and examine who got the largest piece [...] The emphasis is not on quantitative comparison (bigger or smaller), as with bar charts, but on the part of the whole (percentages)." (Alex Kolokolov & Maxim Zelensky, "Data Visualization with Microsoft Power BI", 2024)
"A pie chart is quite simple to create, and sometimes you may want to add a unique feature or 'cherry on the pie'. However, experiments with such traditional visualizations often lead to unsuccessful results. For classic visualizations, it’s best to follow the principle of 'one thought, one chart'.” (Alex Kolokolov & Maxim Zelensky, "Data Visualization with Microsoft Power BI", 2024)
"Pie and donut charts have the same purpose - visualizing the structure for a small number of categories (usually no more than six). These charts are built using the same parameters, with the only difference being that the donut chart has an inner space. They don’t have x-and yaxes, and for customization, you need to follow simple steps." (Alex Kolokolov & Maxim Zelensky, "Data Visualization with Microsoft Power BI", 2024)
"Pie charts, donut charts, and meter charts are really just stacked bar charts that have been bent—but remember that they should always add up to 100%. Radar charts use angle to show categories and position to show amounts. You can also use angle with position to create charts that show movement, direction, or change - on maps and on graphs with number axes, as well as on visualizations with category axes." (Nancy Organ, "Data Visualization for People of All Ages", 2024)
