Kees Goudswaard

The destruction of an endemic species flock: quantitative data on the decline of the haplochromine cichlids of Lake Victoria

SynopsisThe Lake Victoria fish fauna included an endemic cichlid flock of more than 300 species. To boost fisheries, Nile perch (Lates sp.) was introduced into the lake in the 1950s. In the early 1980s an explosive increase of this predator was observed. Simultaneously, catches of haplochromines decreased. This paper describes the species composition of haplochromines in a research area in the Mwanza Gulf of Lake Victoria prior to the Nile perch upsurge. The decline of the haplochromines as a group and the decline of the number of species in various habitats in the Mwanza Gulf was monitored between 1979 and 1990. Of the 123+ species originally caught at a series of sampling stations ca. 80 had disappeared from the catches after 1986. In deepwater regions and in sub-littoral regions haplochromine catches decreased to virtually zero after the Nile perch boom. Haplochromines were still caught in the littoral regions where Nile perch densities were lower. However, a considerable decrease of species occurred in these regions too. It is expected that a remnant of the original haplochromine fauna will survive in the littoral region of the lake. Extrapolation of the data of the Mwanza Gulf to the entire lake would imply that approximately 200 of the 300+ endemic haplochromine species have already disappeared, or are threatened with extinction. Although fishing had an impact on the haplochromine stocks, the main cause of their decline was predation by Nile perch. The speed of decline differed between species and appeared to depend on their abundance and size, and on the degree of habitat overlap with Nile perch. Since the Nile perch upsurge, the food web of Lake Victoria has changed considerably and the total yield of the fishery has increased three to four times. Dramatic declines of native species have also been observed in other lakes as a result of the introduction of alien predators. However, such data concern less speciose communities and, in most cases, the actual process of extinction has not been monitored.

International Trends in Income Inequality and Social Policy

In most OECD-countries income inequality has increased during the last two decades. In this paper, we investigate whether changes in the overall distribution of income can be attributed to social policy measures. For most (but not all) countries we find a possible relationship between changing welfare state policies (as measured by expenditure ratios and replacement rates) and changing income inequality. Especially the United Kingdom and the Netherlands combined an above-average rise in inequality with a reduction in the generosity of the welfare system.A more elaborate budget incidence analysis for the Netherlands indicates that in the period 1981–1997 inequality of disposable household income increased sharply. The two main forces behind this phenomenon were a more unequal distribution of market incomes and changes in social transfers. Fundamental social security reforms in the Netherlands indeed seem to have made the income distribution less equal. However, income inequality in the Netherlands is still below the OECD average at the end of the observed period.

Patterns of welfare state indicators in the EU : Is there convergence?

Convergence of social protection objectives and policies in Member States is an explicit objective of the EU. Earlier research has shown that there has indeed been a tendency of convergence of social protection levels over the last decades. However, comparative studies frequently use indicators which may not be representative as measures of the welfare state. In this article we have done several convergence tests with the most recent data, using a variety of indicators of social protection: social expenditures, both at the macro and at the programme level, replacement rates of unemployment and social assistance benefits and poverty indicators. Together, these indicators provide a broader picture of the evolution of social protection. Our results are less clear cut than earlier findings. We still find convergence of social expenditure in EU countries over a longer period. However, this trend seems to have stagnated in recent years. The evidence is mixed for the other indicators. Replacement rates of unemployment benefits converged to a higher level, but social assistance benefits did not. Poverty rates and poverty gaps have converged since the mid-1980s, but the levels of both indicators have developed in the opposite direction.

On the Convergence of Social Protection Systems in the European Union

Member states of the European Union are autonomous when it comes to the design of their social protection systems. However, they are committed by a Recommendation accepted by the European Council addressing the convergence of social protection objectives and policies. Beside that, it is expected that convergence of social protection systems could come about as a result of economic integration. In this paper we have examined whether such convergence has occurred during the past decades, using data on replacement rates and social expenditure ratios. We find a rather strong trend of relative convergence, but it does not follow that this trend is the result of the European integration.

Progression and revenue effects of income tax reform

Usually, only initial revenue effects of personal income tax reforms are considered. However, a tax reform characterized by base broadening in exchange for rate reduction can reduce the income elasticity of tax revenue. In that case, the increase in revenue after income growth will be relatively smaller: the tax reform has a negative effect on revenue in the second period. Using the microtax model of the Central Planning Bureau we simulated the effects of the Dutch “Oort” reform 1990 on revenue elasticities and, consequently, on tax revenue. The income tax revenue elasticity declined by 17 percent which caused an additional revenue loss of 0.6 percent in 1990, rising to 3.8 percent in 1993.

The redistributive effect of social transfer programmes and taxes: A decomposition across countries

The aim of this article is to offer detailed information of the redistributive impact of social transfer programmes and taxes in 28 Member countries of the Organisation for Economic Co-operation and Development, employing data that have been computed from the Luxembourg Income Studys micro-level database. We find that welfare states on average reduce inequality by 35 per cent. Social benefits have a much stronger redistributive impact than taxes. As far as social programmes are concerned, public pensions account for the largest reduction in income inequality, although the pattern is diverse across countries. To a lesser extent, social assistance, disability and family benefits also contribute to smaller income disparities.

Effects of Nile perch (Lates niloticus) introduction into Lake Victoria, East Africa, on the diet of Pied Kingfishers (Ceryle rudis)

In recent years the ichthyofauna of Lake Victoria, the worlds largest tropical lake, has gone through dramatic changes. The population of Nile perch, a large predator which has been introduced into the lake by man, increased explosively at the expense of many haplochromine cichlid species. At the same time, numbers of a small cyprinid (dagaa) rose sharply.Previously Pied Kingfishers on Lake Victoria fed mainly on haplochromines. Only the youngest nestlings depended on dagaa as primary food. The current diet of adult birds clearly reflects the changes which have occurred in the fish community. Pellet analysis reveals a shift towards a diet composed of almost 100% dagaa.The change in prey species composition has increased the number of fish a kingfisher needs to catch daily in order to meet its energetic demands, because:(1)the mean size of haplochromines is larger than that of dagaa;(2)(2) the mean size of dagaa has decreased since the increase in Nile perch;(3)(3) the weight of dagaa is lower than that of haplochromines of equal size;(4)(4) mainly juvenile dagaa and adults in poor condition are accessible to kingfishers.

The Redistributive Effect of Public and Private Social Programmes: A Cross-Country Empirical Analysis

A function of many national social protection systems is to substantially redistribute income. However, the size and nature of social protection programmes are changing. In a number of countries there has been a shift from public towards private social protection arrangements, with the latter substituting for, or complementing, public programmes. Developing earlier work, this present article analyses the redistributive impact on income of public versus private social protection programmes. Using recent data from the Organisation for Economic Co-operation and Development, we find a strong positive relationship between public social expenditures and income redistribution across countries. For private social expenditures, we find a weak, but statistically significant, negative relationship with the level of redistribution. In countries where a larger share of total social expenditure is accorded to private arrangements there is less income redistribution. We conclude that the choice between the relative weight of public and private provision of social protection affects the redistributive impact of the welfare state.

Measuring retirement savings adequacy : developing a multi-pillar approach in the Netherlands

The Dutch pension system is highly ranked on adequacy. These rankings, however, are based on fictitious replacement rates for median income earners. This paper investigates whether the Dutch pension adequacy is still high when we take into account the resources that people really accumulate, using a large administrative data set. A comprehensive approach is followed: not only public and private pension rights, but also private savings and housing wealth are taken into account. Summed over all age- and socioeconomic groups we find a median gross replacement rate of 83% and a net replacement rate of 101%. At retirement age, 31% of all households face a gross replacement rate that is lower than 70% of current income. Public and occupational pensions each account for more than 35% of total pension annuities. Private non-housing assets account for 14% and imputed rental income from net housing wealth accounts for about 10%. Some vulnerable groups, such as the self-employed, have below average replacement rates. Results are fairly similar to results found in the UK, indicating that we should be careful in evaluating the adequacy of pensions systems on the basis of fictitious replacement rates.

The shift to smaller zooplankton in Lake Victoria cannot be attributed to the 'sardine' Rastrineobola argentea(Cyprinidae)

After the population increase of introduced Nile perch (Lates niloticus) in Lake Victoria, a decrease in the relative abundance of herbivorous cladocerans and calanoids was reported for the pelagic zone. The shift from large herbivores to small-bodied predatory cyclopoids has been attributed to the increase of the zooplanktivorous cyprinid dagaa (Rastrineobola argentea), which rose concomitantly with the Nile perch. However, we observed that in the Mwanza Gulf of the lake cyclopoids dominated the zooplankton community already before the rise of dagaa. Furthermore, there are indications that dagaa takes fewer calanoids than expected from their representation in the environment, although a slight preference for cladocerans may exist. Calanoids dominated the diet of small Nile perch of about 4 cm length, but juvenile Nile perch did not occur in the study area until after the size shift in zooplankton. The lumped biomass of dagaa and small Nile perch is lower than the biomass of the original haplochromine-dominated community of zooplanktivorous fish. Thus, the decline of large zooplankters in the lake cannot be explained by intensified predation after the replacement of zooplanktivorous haplochromines by dagaa and Nile perch. Increased eutrophication, resulting in a shift in predominance from diatoms to cyanophytes, is suggested as an alternative explanation for the shift in zooplankton composition.