Show Me the Numbers Designing Tables and Graphs to Enlighten (Stephen Few) (z-library.sk, 1lib.sk, z-lib.sk)

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Show Me the NuMberS

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Show Me the NuMberS Designing tables and Graphs to enlighten SecoND eDitioN StepheN Few Analytics Press burliNGaMe, caliForNia

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Analytics Press po box 1545 burlingame, ca 94011 SaN 253-5602 www.analyticspress.com email: info@analyticspress.com © 2012 by Stephen c. Few all rights reserved. protected under the berne convention. publiSher: Jonathan G. Koomey copY eDitor: Nan wishner coMpoSitioN: bryan pierce coVer DeSiGN: Stephen Few photoGraphY: John Fernez priNter aND biNDer: c&c offset printing company reproduction or translation of any part of this work in any form or by any means, electronic or mechanical, beyond that permitted by Section 107 or 108 of the 1976 united States copyright act without the expressed permission of the copyright owner is unlawful. requests for permission or further information should be addressed to analytics press at the address or url above. iSbN-10: 0-9706019-7-2 iSbN-13: 978-0-9706019-7-1 this book was printed on acid-free paper in china. 10 9 8 7 6 5 4 3 2 1

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if we’ve done well in life, we have fellow travelers to thank. No one succeeds alone. in my life’s story, many of the heroes are teachers. Several extraordinary educators from elementary school through graduate school invited me into a world of never-ending wonder and gave me the confidence to make it my own. More than the content of their lessons, what influenced me most were the ways they found to connect with me as a person who was worthy of their time. their remarkable kindness, commitment to education, and practiced skill helped me become the person, and the teacher, that i am today. if i’ve done and can continue to do for others what these teachers have done for me, my life has meaning.

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Oh, the thirst to know how many! The hunger to know how many stars in the sky! We spent our childhood counting stones and plants, fingers and toes, grains of sand, and teeth, our youth we passed counting petals and comets’ tails. We counted colors, years, lives, and kisses; in the country, oxen; by the sea, the waves. Ships became proliferating ciphers. Numbers multiplied. The cities were thousands, millions, wheat hundreds of units that held within them smaller numbers, smaller than a single grain. Time became a number. Light was numbered and no matter how it raced with sound its velocity was 37. Numbers surrounded us. When we closed the door at night, exhausted, an 800 slipped beneath the door and crept with us into bed, and in our dreams 4000s and 77s pounded at our foreheads with hammers and tongs. 5s added to 5s until they sank into the sea or madness, until the sun greeted us with its zero and we went running to the office, to the workshop, to the factory, to begin again the infinite 1 of each new day. excerpt from the poem “ode to Numbers” by pablo Neruda, Selected Odes of Pablo Neruda, translated by Margaret Sayers peden (1995). university of california press.

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PrefAce to Second edition xv 1. introduction 1 The use of tables and graphs to communicate quantitative information is common practice in organizations today, yet few of us have learned the design practices that make them effective. This introductory chapter prepares the way for a journey of discovery that will enable you to become an exception to this unfortunate norm. purpose 8 Scope 9 intended readers 11 content preview 11 communication style 12 2. SiMPLe StAtiSticS to Get You StArted 15 Quantitative information forms the core of what organizations must know to operate effectively. The current emphasis on metrics, Key Performance Indicators (KPIs), Balanced Scorecards, and performance dashboards demonstrates the importance of numbers to organizations today. Stories contained in numbers can be communicated most effectively when we understand the fundamental characteristics and meanings of simple statistics that are routinely used to make sense of numbers, as well as the fundamental principles of effective communication that apply specifically to quantitative information. Quantitative relationships 15 Numbers that summarize 21 Measures of money 35 3. differinG roLeS of tABLeS And GrAPHS 39 Tables and graphs are the two fundamental vehicles for presenting quantitative information. They have developed over time to the point that we now thoroughly understand which works best for different circumstances and why. This chapter introduces tables and graphs and gives simple guidelines for selecting which to use for your particular purpose. Quantities and categories 40 choosing the best medium of communication 42 tables defined 43 when to use tables 44 Graphs defined 45 a brief history of graphs 46 when to use graphs 48 coNteNtS

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x S h o w M e t h e N u M b e r S 4. fundAMentAL VAriAtionS of tABLeS 53 Tables should be structured to suit the nature of the information they are meant to display. This chapter breaks tables down into their fundamental variations and provides simple rules of thumb for pairing your message with the best tabular means to communicate it. relationships in tables 53 Variations in table design 57 table design solutions 59 5. ViSuAL PercePtion And GrAPHicAL coMMunicAtion 61 Because graphical communication is visual, it must express information in ways that human eyes can perceive and brains can understand. Our eyes and the parts of the brain that handle input from them work in particular ways. Thanks to science, how we see is now fairly well understood, from the initial information-carrying rays of light that enter our eyes to the interpretation of that information in the gray folds of the visual cortex. By understanding visual perception and its application to the graphical communication of quantitative information, you will learn what works, what doesn’t, and why. This chapter brings the principles of graphical design for communication alive in ways that are practical and can be applied skillfully to real-world challenges in presenting quantitative information. Mechanics of sight 63 attributes of preattentive processing 67 applying visual attributes to design 71 Gestalt principles of visual perception 80 6. fundAMentAL VAriAtionS of GrAPHS 87 Different quantitative relationships require different types of graphs. This chapter explores the fundamental variations of graphs that correspond to different quantitative relationships and then pairs these variations with the visual components and techniques that can present them most effectively. encoding data in graphs 87 relationships in graphs 101 Graph design solutions 105 PrActice in SeLectinG tABLeS And GrAPHS 137 Learning requires practice. Through practice you reinforce what you’ve learned by embedding it more securely in your memory and strengthen your ability to make connections between the concepts we’ve examined and their application to the real world.

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co N t e N t S xi 7. GenerAL deSiGn for coMMunicAtion 141 With a basic understanding of visual perception, we can build a set of visual design principles, beginning with those that apply equally to tables and graphs. Our primary visual design objectives will be to present content to readers in a manner that highlights what’s important, arranges it for clarity, and leads them through it in the sequence that tells the story best. highlight 141 organize 144 integrate tables, graphs, and text 148 8. tABLe deSiGn 155 Once you’ve determined that a table should be used to communicate your message and have chosen the type of table that will work best, you should refine your design so that it can be quickly and accurately read and understood. Structural components of tables 155 table design best practices 158 PrActice in tABLe deSiGn 185 Nothing helps learning take root like practice. You will strengthen your developing expertise in table design by working through a few real-world scenarios. 9. GenerAL GrAPH deSiGn 191 The visual nature of graphs requires a number of unique design practices. The volume and complexity of quantitative information that you can communicate with a single graph are astounding but only if you recognize and avoid poor design practices that would undermine your story. Maintain visual correspondence to quantity 191 avoid 3D 197 10. coMPonent-LeVeL GrAPH deSiGn 205 Several visual and textual components work together in graphs to present quantitative information. If these components are out of balance or misused, the story suffers. For each component to serve its purpose, you must understand its role and the design practices that enable it to fulfill its role effectively. primary data component design 205 Secondary data component design 224 Non-data component design 247

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xii S h o w M e t h e N u M b e r S 11. diSPLAYinG MAnY VAriABLeS At once 257 Graphs can be used to tell complex stories. When designed well, graphs can combine a host of data spread across multiple variables to make a complex message accessible. When designed poorly, graphs can bury even a simple message in a cloud of visual confusion. Excellent graph design is much like excellent cooking. With a clear vision of the end result and an intimate knowledge of the ingredients, you can create something that nourishes and inspires. combining multiple units of measure 257 combining graphs in a series of small multiples 259 other arrangements of multi-graph series 268 12. SiLLY GrAPHS tHAt Are BeSt forSAKen 271 Several graphs that are readily available in software fail miserably at data presentation even though their popularity is growing. The stories that people attempt to tell with these graphs can be told simply and clearly using alternatives that are described in this chapter. Donut charts 271 radar charts 272 Stacked area graphs for combining part-to-whole and time-series 275 relationships circle charts 277 unit charts 278 Funnel charts 281 waterfall charts for simple part-to-whole relationships 283 PrActice in GrAPH deSiGn 287 You’ve come far in your expedition into the world of graph design. It’s now time for some practice to pull together and reinforce all that you’ve learned. Expert graph design requires that you adapt and apply what you’ve learned to a variety of real-world communication problems. Working through a few scenarios with a clear focus on the principles of effective graph design will strengthen your expertise and your confidence as well. 13. teLLinG coMPeLLinG StorieS WitH nuMBerS 295 Important stories live in the numbers that measure what’s going on in the world. Before we can present quantitative information, we must first uncover and understand its stories. Once we know the stories, we can tell them in ways that help others to understand them as well. characteristics of well-told statistical stories 297 Stories in the wings 306

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co N t e N t S xiii 14. tHe interPLAY of StAndArdS And innoVAtion 307 When you design tables and graphs, you face many choices. Of the available alternatives, some are bad, some are good, some are best, and others are simply a matter of preference among equally good choices. By developing and following standards for the visual display of quantitative information, you can eliminate all but good choices once and for all. This dramatically reduces the time it takes to produce tables and graphs as well as the time required by your readers to make good use of them. Doing this will free up time to put your creativity to use where it’s most needed. APPendiceS 309 table and Graph Design at a Glance 309 recommended reading 311 adjusting for inflation 313 constructing tables lens Displays in excel 315 constructing box plots in excel 318 answers to practice in Selecting tables and Graphs 322 answers to practice in table Design 325 answers to practice in Graph Design 333 useful color palettes 344 index 345

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preFace to SecoND eDitioN In 1914, ninety years before the first edition of this book was published, Willard C. Brinton wrote what was perhaps the first book about graphical data presenta- tion, entitled Graphic Methods for Presenting Facts. The relatively few books on the topic that have been published since Brinton’s have mostly appeared during the last 20 years. If you read Brinton’s trailblazing book, you will be surprised by how little has changed since he wrote it. The problems that he tried to solve were not so different from those that we face today. Brinton began his book with the following words: After a person has collected data and studied a proposition with great care so that his own mind is made up as to the best solution for the problem, he is apt to feel that his work is about completed. Usually, however, when his own mind is made up, his task is only half done. The larger and more difficult part of the work is to convince the minds of others that the proposed solution is the best one—that all the recommendations are really necessary. Time after time it happens that some ignorant or presumptuous member of a committee or a board of directors will upset the carefully- thought-out plan of a man who knows the facts readily enough to overcome the opposition. It is often with impotent exasperation that a person having the knowledge sees some fallacious conclusion accepted, or some wrong policy adopted, just because known facts cannot be marshaled and presented in such manner as to be effective. Millions of dollars yearly are spent in the collection of data, with the fond expectation that the data will automatically cause the correction of the conditions studied. Though accurate data and real facts are valuable, when it comes to getting results the manner of presentation is ordinarily more important than the facts themselves. The foundation of an edifice is of vast importance. Still, it is not the foundation but the structure built upon the foundation which gives the result for which the whole work was planned. As the cathedral is to its foundation so is an effective presentation of facts to the data.1 Accumulating information in and of itself is not useful. Information can’t possibly serve a purpose until we first identify what’s meaningful and then manage to make sense of it. Even once we understand the information, it remains inert until we actually do something with it. The true promise of the information age isn’t tons of data but decisions and actions that are better because they’re based on an understanding of what’s really going on in the world. Any knowledge that you gain that could be used to make better decisions will amount to nothing if you can’t communicate it to others in a way that 1. willard c. brinton (1914) Graphic Methods For Presenting Facts. the engineering Magazine company, pages 1 and 2.

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xvi S h o w M e t h e N u M b e r S makes sense to them. The ability to find what’s useful in the mounds of data that surround us, to make sense of it, and to then present it clearly and accu- rately, forms the foundation on which the information age will finally fulfill its promise. Unless we give information a clear voice, its important stories will remain unheard, and ignorance will prevail. As I write these words, more than 10 years into the 21st century, I still feel compelled to make the same essential case that Brinton made long ago when he wrote: If an editor should print bad English he would lose his position. Many editors are using and printing bad methods of graphic presentation, but they hold their jobs just the same. The trouble at present is that there are no standards by which graphic presentations can be prepared in accordance with definite rules so that their interpretation by the reader may be both rapid and accurate. It is certain that there will evolve for methods of graphic presentation a few useful and definite rules which will correspond with the rules of grammar for the spoken and written language. The rules of grammar for the English language are numerous as well as complex, and there are about as many exceptions as there are rules. Yet we all try to follow the rules in spite of their intricacies. The principles for a grammar of graphic presentation are so simple that a remarkably small number of rules would be sufficient to give a universal language.2 Even though no precedent for codifying the rules of graphic presentation existed in his day, Brinton made a bold and brilliant attempt to begin this work. Nearly a century has now passed, and in that time I and others have continued the work, resulting in the simple set of rules that Brinton hoped for, but these rules are known by relatively few who need them. In Brinton’s time, the com- puter was still many years in the future. Graphics were produced by hand, usually by professional draftsmen. It is sad that since the advent of the com- puter—especially personal computing, which gave everyone the means to produce graphs and to do so efficiently—the quality of graphical communica- tion has actually diminished. Having the means to create graphs with a com- puter doesn’t guarantee that we’ll do it effectively any more than having word processing software makes us great writers. It seems that we’ve lost sight of this distinction and assume that if we know how to use software that was designed to produce graphs, we have all that we need. Relying on software to do this for us results in failure. Software can do little to help us communicate graphically if we don’t already possess the basic skills to do it ourselves. You might be wondering why I’m writing a new edition of this book only eight years after the first edition was published. Has that much changed? Although relatively few changes have taken place in data visualization, I’ve learned a great deal more than I knew eight years ago. Most of the changes that I’ve made to this new edition are the results of my own professional growth. Show Me the Numbers was the first of three books that I’ve now written. When I wrote it originally I had only recently begun focusing on data visualization 2. ibid., page 3.

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p r e Fa c e xvii despite having worked for nearly 20 years in information technology, mostly in business intelligence. I devoured the work of Edward Tufte and others, compiled the best of it, ran it through the filter of my own experience, then organized and expressed it to address the practical needs of people like you. Since writing the first edition of this book, I have taught data visualization courses internationally to thousands of people, written scores of articles, white papers, and two more books, and have worked with and advised many diverse organizations. As a result, my expertise has matured. This second edition of Show Me the Numbers is the result of this maturity. In addition to my professional development, a few things have been happen- ing in the world that affect graphical communication—some positive, which I describe in this edition, and some negative, which I warn against. On the positive side, two people in particular have shown that important stories involving numbers can be told in compelling ways. Even though Al Gore did not invent data visualization (or the Internet), the compelling nature of the graphical displays in his film An Inconvenient Truth began to change the tide of opinion about global warming. Those graphical displays moved people thanks to expert assistance from Nancy Duarte and Duarte Design. Another person who has used graphics to capture the imaginations of many in recent years is Hans Rosling of GapMinder.org. When this Swedish professor took the stage at the 2006 Technology, Entertainment, and Design (TED) Conference and told a story about the relationship between fertility and life expectancy throughout the world from 1962 to the present using an animated bubble chart, a new era of quantitative storytelling began. On the negative side, the availability of bad graphs has increased since the first edition of this book. This expansion of bad graphical presentation has been made possible by the Web and has been fueled by uninformed so-called experts and self-serving software vendors. During the past few years, the number of people who claim expertise in data visualization has increased dramatically, but unfortunately many of them do not exhibit best practices. This is especially true of many graphic artists whose data-based visualizations are greeted with fanfare even though they don’t actually inform, or do so poorly. Flashy visual displays are engaging, but unless they invite people to think about data in meaningful ways that lead to understanding, they fail in their purpose. Nothing has been more disappointing to me personally than the lack of improvement in the charting capabilities of the product that is used more than any other to produce graphs: Microsoft Excel. The 2007 and 2010 releases of Excel have added superficial sizzle to the product’s graphs without addressing any of the fundamental charting problems that have existed for years. Excel still encourages people to produce bad graphs—in some respects more than in the past because it now offers even more dysfunctional choices. Nevertheless, because practically everyone in the world who produces graphs has a copy of Excel, I’ve made a point of featuring graphs in this book that can be created effectively with Excel if you know what you’re doing. Fortunately, the necessary skills are quite simple and easy to learn.

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xviii S h o w M e t h e N u M b e r S The purpose of this book is to help people present quantitative information in the most informative way possible, using simple skills and tools that are readily available. I invite you to enjoy the journey of learning these essential skills.