Cascades of Failure and Extinction in Evolving Complex Systems

There is empirical evidence from a range of disciplines that as the connectivity of a network increases, we observe an increase in the average fitness of the system. But at the same time, there is an increase in the proportion of failure/extinction events which are extremely large. The probability of observing an extreme event remains very low, but it is markedly higher than in the system with lower degrees of connectivity. We are therefore concerned with systems whose properties are not static but which evolve dynamically over time. The focus in this paper, motivated by the empirical examples, is on networks in which the robustness or fragility of the vertices is not given, but which themselves evolve over time We give examples from complex systems such as outages in the US power grid, the robustness properties of cell biology networks, and trade links and the propagation of both currency crises and disease. We consider systems which are populated by agents which are heterogeneous in terms of their fitness for survival. The agents are connected on a network, which evolves over time. In each period agents take self-interested decisions to increase their fitness for survival to form alliances which increase the connectivity of the network. The network is subjected to external negative shocks both with respect to the size of the shock and the spatial impact of the shock. We examine the size/frequency distribution of extinctions and how this distribution evolves as the connectivity of the network grows. The results are robust with respect to the choice of statistical distribution of the shocks. The model is deliberately kept as parsimonious and simple as possible, and refrains from incorporating features such as increasing returns and externalities arising from preferential attachment which might bias the model in the direction of having the empirically observed features of many real world networks. The model still generates results consistent with the empirical evidence: increasing the number of connections causes an increase in the average fitness of agents, yet at the same time makes the system as whole more vulnerable to catastrophic failure/extinction events on an near-global scale.Agent-Based Model; Connectivity; Complex Systems; Networks

The Public Renders a Split Verdict on Changes in Family Structure

Analyzes views on family and increases in unmarried or gay and lesbian couples and single women raising children, unmarried couples living together, mothers of young children working outside the home, interracial marriages; and women not having children

Who Moves? Who Stays Put? Where's Home?

Analyzes results of a Pew Social & Demographic Trends survey on Americans' geographic mobility, including perceptions of "home," reasons for moving or staying, and economic considerations, by race/ethnicity, education, region, and other demographics

Illegal Immigration Backlash Worries, Divides Latinos

Compares survey responses of Latinos/Hispanics with those of the general population and by nativity on topics such as immigration policy, illegal immigrants' impact on other Latinos/Hispanics, and political solidarity between the native- and foreign-born

Democratic theory and constitutional change in South Africa

African Studies Seminar series. Paper presented 1990In the last two years the debate on democracy in South Africa has reached a new intensity. The unbanning of the ANC and other opposition movements occurred at the same time as the Cold War in Europe came to an end. Countries such as Poland, Czechoslovakia and Hungary that had for decades been ruled by totalitarian regimes began to be transformed by popular political pressure. Demands for democratic change also escalated in South Africa during the 1980s. It finally lead the South African government of F.W. De Klerk to announce in February 1990 the unbanning of the ANC, PAC and other opposition liberation movements and the release of Nelson Mandela from jail. The following year the government established the Convention for a Democratic South Africa (CODESA) in order to negotiate a new constitution. The pace of the changes has caught many political analysts unawares. Craig Charney has suggested that the failure of political scientists to predict the new turn of events indicated wider methodological shortcomings. Much political science analysis of South Africa in the 1980s was still dominated, Charney has argued, by a failure to see politics as an autonomous activity rather than as simply a receptacle for social groups. This often results in crude theories of the state that fail to consider it as an actor in its own right. Moreover many political scientists still have an overly-simplistic view of model building that depend more on comparisons with the metropolitan core of Europe and North American than other developing regimes in Latin American and Asia. These criticisms suggest that new approaches are needed to explain South African political changes. The role of democracy in South African politics especially is still rather poorly understood by analysts despite the fact that it has played a prominent role in political discourse since at least the 1950s. Building a democratic state and society in South Africa is now central, to the current South African political agenda, though so far little work has been done to explore this in a comparative perspective. This paper will therefore examine the state of democratic thinking in South Africa and the conditions that could lead to the creation of some form of democratic regime. In the first part, it will examine the current state of theoretical debate over what democracy is both as an ideology and as a description of a particular kind of political regime. The second part of the paper will then discuss the evolution of debate over democracy in South African politics. Finally, the third part of the paper will look at how a South African democratic transition might occur through a process of political bargaining, taking into consideration similar processes in other regimes moving out of political authoritarianism. The methodological approach of this paper is one that seeks to learn from the past both in terms of the general formulation of democratic theory and its application to South African conditions. Hitherto social analysts and historians have tended to be preoccupied with the genesis and development of different concepts in South African politics such as segregation, liberalism, apartheid and nationalism. Democracy has frequently been seen as tangential to these other doctrines despite its considerable impact on political debate. The emergence of a new international climate favourable to democratisation following the end of the Cold War offers up the opportunity for a re-evaluation of the South African past in terms of democratic ideas and values

Liberals, radicals and the politics of black consciousness, 1969-1976

African Studies Seminar series. Paper presented 24 July 1989. Not to be quoted without the Author's permission.The period from the demise of the Liberal Party in 1968, following the introduction of the Prohibition of Political Interference Act, to the 1976 Soweto students revolt can be seen as an important transitional period in South African politics that requires re-evaluation by students of contemporary history. These years mark in particular the eclipse of a tradition of paternalistic welfare liberalism in South Africa stretching back to the inter-war years and the foundation of the South African Institute of Race Relations in 1929. At the same time they also pinpoint the re-emergence of a tradition of democratic radicalism anchored around the Freedom Charter after its initial suppression at the time of the State of Emergency in 1960 and the banning of the P.A.C. and A.N.C. These two traditions have often confused in the minds of some analysts and a recent volume of essays has effectively sought to claim most of the recent phase of liberalism in South Africa in terms of a programme of democratic participation, despite the refusal of the Liberal party to take part in the organisation behind the freedom Charter in 1955

Liberalism and ethnicity in South African politics, 1921-1948

African Studies Seminar series. Paper presented March 1976One of the main problems confronting liberal ideology in the South African context is the nature and role of group identities. This has been no small question because liberal theorists have tended to be hide-bound by a reliance on the inherent rationality of a free market that specifically excludes the role of group interests from its sphere of operations. Thus, while twentieth century liberalism has made a number of important revisions in the classical laissez-faire model of the nineteenth century, it still places a considerable emphasis on the free market sector even though, as Professor John Kenneth Galbraith has observed, this now typifies only a minority sector in western capitalist economies. It is this dependency on the free-market model, however, that restricts the liberal view of rationality to one of economics. The most rational figure in this view remains the classic homo economicus, the child of the Eighteenth Century Enlightenment, who buys in the cheapest market and sells in the dearest. The implications of this model are far-reaching in terms of social values. If the basis of society is seen to rest on free-floating individuals motivated by a high degree of psychological hedonism then the basis of society's values rests on individual ones to the neglect of the wider community. This is perhaps one reason why capitalist societies in the west have had such difficulty, for example, in regulating and controlling firms involved in spreading pollution: the traditional free-market model only assumes a relationship between buyer and seller and cannot account for a third party involved in the transaction in the form of the community. Moreover, in terms of its system of morality, liberalism relies on a general public good accruing from the actions of individuals: by some mysterious hidden hand, "public good" is assumed to emerge from "private vices". As Robert Paul Wolff has argued, liberalism is unable to make the jump, short of radical revision, from the notion of a private value to one of community. Utilitarianism, he argues, in its concern for the greatest happiness for the greatest number, rests only on private values and a development of liberalism towards the direction of interpersonal values is the only way of resolving this problem and developing a liberal morality that recognises the existence of a wider community

The Agrarian counter-revolution in the Transvaal and the origins of segregation: 1902-1913

African Studies Seminar series. Paper presented June 1975This paper seeks to examine the circumstances surrounding the rise of a segregationist ideology in South Africa during the decade after the Boer War, culminating in the Natives’ Land Act of 1913. In tracing this development, the approach is essentially one of establishing a relationship between the underlying structures that made segregation materially possible and the cleavages within the white political system that increasingly drove the polity towards an ideology of segregation