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Diversity and Complexity

Diversity and Complexity

Scott E. Page
Copyright Date: 2011
Pages: 296
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  • Book Info
    Diversity and Complexity
    Book Description:

    This book provides an introduction to the role of diversity in complex adaptive systems. A complex system--such as an economy or a tropical ecosystem--consists of interacting adaptive entities that produce dynamic patterns and structures. Diversity plays a different role in a complex system than it does in an equilibrium system, where it often merely produces variation around the mean for performance measures. In complex adaptive systems, diversity makes fundamental contributions to system performance.

    Scott Page gives a concise primer on how diversity happens, how it is maintained, and how it affects complex systems. He explains how diversity underpins system level robustness, allowing for multiple responses to external shocks and internal adaptations; how it provides the seeds for large events by creating outliers that fuel tipping points; and how it drives novelty and innovation. Page looks at the different kinds of diversity--variations within and across types, and distinct community compositions and interaction structures--and covers the evolution of diversity within complex systems and the factors that determine the amount of maintained diversity within a system.

    Provides a concise and accessible introductionShows how diversity underpins robustness and fuels tipping pointsCovers all types of diversityThe essential primer on diversity in complex adaptive systems

    eISBN: 978-1-4008-3514-0
    Subjects: Political Science, Sociology

Table of Contents

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  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-viii)
    (pp. ix-xii)
    (pp. 1-15)

    In writing this book, I have been fortunate to be guided and motivated by the efforts of an incredible collection of scholars. The study of diversity and complexity attracts a vast array of scholars from multiple disciplines whose passion, intelligence, and energy inspire awe. In what follows, I attempt to pull together ideas, concepts, models, and results that intersect with the topics of diversity and complexity, and to make sense of research from multiple disciplines. It proves a daunting, humbling, and ultimately, exciting task.

    The book combines illustrative examples, formal models, and bits of data to produce an overview of...

    (pp. 16-53)

    In this chapter, I pose and answer some basic questions. What is diversity? What is complexity? And, why link diversity and complexity—what does one have to do with the other? First, diversity. Diversity applies to populations or collections of entities. A ball bearing cannot be diverse. Nor can a flower. Diversity requires multitudes. Cities are diverse; they contain many people, organizations, buildings, roads, etcetera. Ecosystems are diverse because they contain multiple types of flora and fauna.

    When scientists speak of diversity, they can mean any of three characteristics of a population. They can meanvariationin some attribute, such...

    (pp. 54-78)

    To move beyond loose, informal characterizations of diversity requires formal measures. Without measures, we can at best make qualitative comparisons.11Any foray into measures obliges the reader to acquire notation, definitions, and subtle distinctions that may lack immediate context and lends an austerity to the text, but so be it. My intent is not to discourage all but the most persistent readers, but to build a common vocabulary and basis of knowledge.

    Counting the number of types is the most obvious way to measure diversity. Ecologists refer to this asspecies richness.Types, though, may not be well defined, a...

    (pp. 79-126)

    The natural world supports incredible diversity: there are more than thirty thousand species of ants and millions of species of beetles. The British scientist J.B.S. Haldane reputedly once quipped, “the Creator, if he exists, has an inordinate fondness for beetles.” The world constructed by humans has amazing diversity as well: we produce approximately one million new books each year and probably at least that many new recipes, including (I’m not making this up) Captain Crunch Chicken. Diversity abounds, but it has limitations. Only a few hundred species of hummingbirds exist, and despite millions of computer programmers, only a handful of...

    (pp. 127-147)

    In this chapter I take up the question of why we see tremendous diversity in some places and not so much in others. For example, why thousands of species of trees but only two species of elephants? Why do rolls of household toilet paper come in one size, while facial tissue is packaged in a range of sizes from larger than a breadbox to smaller than a deck of cards? Why so many species of beetles but a mere fifty or so of rats? And, finally, why so much differentiation in the wood and steel skeletons that support our architectural...

    (pp. 148-166)

    In this chapter I focus on the roles that variation plays in complex systems. Prior to taking on that topic, I provide some scaffolding for what’s to follow. One of my main points will be that variation enhances system level robustness. Therefore, it’s necessary first to clarify the concept of robustness and to distinguish it from stability. Robustness is often not given the depth of analysis it deserves. Here I do not attempt a comprehensive survey of the literature on the topic (see Jen 2005; Levin 2000; Krakauer 2005): I simply get a few of the main ideas out on...

    (pp. 167-182)

    I now begin an analysis of the effects of diverse types on complex systems. I start with two (almost) inescapable benefits of diversity. These benefits go a long way toward explaining why scientifically minded people believe in the value of diversity. They explain why scientists and laypeople alike concerned with the preservation of ecosystems speak about the importance of species preservation. And why investment advisors talk about the importance of balanced portfolios.

    These inescapable benefits result from two causes: averaging and diminishing returns to type. The first cause, averaging, refers to the fact that if you have lots of types,...

    (pp. 183-195)

    In this chapter, I show how diminishing returns to type provide a second inescapable benefit of diversity. When diminishing returns to type are present, diverse collections do best. Suppose we had an empirical question as to whether diversity improves performance in some context. We may want to understand whether racial or gender diversity improves group problem solving efficiency, whether species diversity enhances ecological robustness, or whether economic diversity increases productivity. As long as diminishing returns are present, we’ll usually find a benefit to diversity.

    Diminishing returns to type exist if the contribution to some performance measure such as efficiency, robustness,...

    (pp. 196-248)

    In the previous two chapters I showed how diversity can improve system performance through averaging and diminishing returns to type. Those results assumed limited interactions between diverse types, and therefore few or no synergies. In this chapter, I describe the myriad ways in which diversity impacts complex systems when interactions are present.

    I demonstrate how diversity enables systems to flourish, to be robust, and also touch on efficiency and innovativeness. Clearly, to be robust a system must have some level of efficiency and must be able to innovate in the face of change, so these effects will be related. My...

    (pp. 249-256)

    In this book, I have introduced definitions and measures of diversity and relied on simple models to explore the effects of diversity in complex systems. I’ve devoted less time to empirical facts about levels of diversity in economic, social, and biological systems. I chose that path not because I deem the facts unimportant. To the contrary, I agree with Deborah Gordon (2010) and others that advances in complex systems research require deep, accurate empirical investigations. However, given the breadth of the topic at hand, I felt the best approach was to provide a common vocabulary and to identify those effects...

    (pp. 257-270)
  15. NOTES
    (pp. 271-280)
  16. INDEX
    (pp. 281-291)