Assessing farmer behaviour as affected by policy and technological innovations: bio-economic farm models

Farm Management,

Unexpected understorey community development after 30 years in ancient and post-agricultural forests

1. Land-use change is considered one of the most radical and extensive disturbances that have influenced plant distributions and diversity patterns in forest understorey communities in much of Europe and eastern North America. In forests growing on former agricultural land, local species diversity and community differentiation among sites are generally reduced compared to ancient forests (i.e. forests with no historical record of agriculture). Yet, no study has determined how the compositional differences created by former land use change over time as the forest sites recover from former agricultural use. 2. Here we resurveyed 78 vegetation plots (half of the plots in ancient and half in post-agricultural forest) to demonstrate how three decades of forest development have changed the compositional differences between post-agricultural and ancient forest sites. The impact of land-use history and survey date was tested on two measures of species diversity and two measure of community divergence. 3. The data indicate that the imprint of former agricultural land use persisted over time, yet not through compositional stability. Parallel and strong vegetation shifts occurred in both ancient and post-agricultural forest: the species diversity decreased and local species cover strongly diverged, which indicates community drift. The observed understorey changes did thus not support the commonly accepted model of community development in post-agricultural forests, i.e. the diversity did not increase and the vegetation did not become more similar to the ancient forest vegetation over time. The changes in species composition were associated with an increase of common, competitive species at the expense of ancient forest indicator species. The source populations of ancient forest species have been gradually depleted, so the recovery of post-agricultural forests becomes even more precarious. 4. Synthesis. While land-use history is likely to persist as the primary predictor of local species diversity and community divergence, other environmental drivers may additionally structure forest understorey communities and lead to biotic impoverishment and pervasive species reordering on the time scale of only decades

Business ownership and economic growth: an emperial investigation

Studie naar de relatie tussen het aantal zelfstandige ondernemers en economische groei. Onderzocht wordt het bestaan van een lange termijn relatie tussen het aantal ondernemers en de fase van economische ontwikkeling. Daarnaast wordt ingegaan op het feit dat zelfstandige ondernemerschap aantrekkelijker wordt doordat een daling van de economische groei leidt tot hoge werkloosheid. Lage werkloosheid stimuleert mensen, die het moeilijk hebben om een baan te vinden of wiens cariëre bedreigt wordt in bestaande ondernemingen, om zelfstandige ondernemer te worden.� Dit leidt tot een omgekeerde�effect van de invloed van economische groei� op het aantal zelfstandige ondernemers per beroepsbevolking.

The relationship between economic development and business ownership revisited

This paper revisits the two-equation model of Carree, van Stel, Thurik and Wennekers (2002) where deviations from the 'equilibrium' rate of business ownership play a central role determining both the growth of business ownership and that of economic development. Two extensions of the original setup are addressed: using longer time series of averaged data of 23 OECD countries (up to 2004) we can discriminate between different functional forms of the 'equilibrium' rate and we allow for different penalties for being above or under the 'equilibrium' rate. The additional data do not provide evidence of a superior statistical fit of a U-shaped 'equilibrium' relationship when compared to an L-shaped one. There appears to be a growth penalty for having too few business owners but not so for having too many.

Age, period and cohort effects on migration of the baby boomers in Australia

The differential migration behaviour of the baby boom generation is commonly explained by reference to cohort size effects. This paper focuses on inter-cohort differences in the intensity and pattern of internal migration in Australia, while paying particular attention to the Australian baby boomer generation as it has moved through the life-course. A series of generalised linear models are fitted to migration transition for age-period-cohort spaces to disentangle the effects of age, period and birth cohort on migration. The results demonstrate that the relative contribution of age to change in migration intensity is largest in relative terms, followed by cohort, while the effects of period were much more subtle. In comparison to earlier work on cohort effects in the United States that showed a negative effect of large cohort size on migration, cohort effects on migration are not restricted to the baby boom but show a continuous upwards trend across cohorts. We find that this divergence from the US-based evidence regarding cohort effects is largely due to the different timing and magnitude of the Australian baby boom compared to the US. The baby boom in Australia was delayed and much smaller in terms of absolute and relative cohort size than in the US. Results highlight the importance of factors other than cohort size, such as differences in attitudes to mobility and housing market dynamics, in shaping migration behaviour of the Australian baby boomers

The relationship between entrepreneurship and economic development: is it U-shaped?

Following a centuries-long decline in the rate of self-employment, a discontinuity in this downward trend is observed for many advanced economies starting in the 1970s and 1980s. In some countries the rate of self-employment appears to increase. At the same time, cross-sectional analysis shows a U-shaped relationship between start-up rates of enterprise and levels of economic development. We provide an overview of the empirical evidence concerning the relationship between independent entrepreneurship, also known as self-employment or business ownership, and economic development. We argue that the reemergence of independent entrepreneurship is based on at least two ‘revolutions’. If we distinguish between solo selfemployed at the lower end of the entrepreneurship spectrum, and ambitious and/or innovative entrepreneurs at the upper end, many advanced economies show a revival at both extremes. Policymakers in advanced economies should be aware of both revolutions and tailor their policies accordingly.  

Information-theoretic analysis of the directional influence between cellular processes

Inferring the directionality of interactions between cellular processes is a major challenge in systems biology. Time-lagged correlations allow to discriminate between alternative models, but they still rely on assumed underlying interactions. Here, we use the transfer entropy (TE), an information-theoretic quantity that quantifies the directional influence between fluctuating variables in a model-free way. We present a theoretical approach to compute the transfer entropy, even when the noise has an extrinsic component or in the presence of feedback. We re-analyze the experimental data from Kiviet et al. (2014) where fluctuations in gene expression of metabolic enzymes and growth rate have been measured in single cells of E. coli. We confirm the formerly detected modes between growth and gene expression, while prescribing more stringent conditions on the structure of noise sources. We furthermore point out practical requirements in terms of length of time series and sampling time which must be satisfied in order to infer optimally transfer entropy from times series of fluctuations.Comment: 24 pages, 7 figure