Getting the Best of Both Worlds? Developing Complementary Equation-Based and Agent-Based Models

We argue that building agent-based and equation-based versions of the same theoretical model is a fruitful way of gaining insights into real-world phenomena. We use the epistemological concept of “models as isolations and surrogate systems” as the philosophical underpinning of this argument. In particular, we show that agent-based and equation-based approaches align well when used simultaneously and, contrary to some common misconceptions, should be considered complements rather than substitutes. We illustrate the usefulness of the approach by examining a model of the long-run relationship between economic development and inequality (i.e., the Kuznets hypothesis)

Productive integration, economic recession and employment in Europe: an assessment based on vertically integrated sectors

The Covid-19 crisis has revamped the discussion about the redefinition of GVC. This paper contributes to the debate, analysing the productive relationships between European countries in four key manufacturing activities. In particular, the paper addresses two objectives. First, it maps the degree of productive integration in Europe, focusing on the generation of employment in the production of exported intermediate inputs and final goods. Second, it provides a preliminary assessment of the potential impact on employment that the current economic crisis will have on some manufacturing activities across Europe. The analysis is realised employing the concept of vertically integrated labour (Pasinetti 1973) which allows to account for the employment directly and indirectly involved in the production of final goods. The estimations are derived from Multi-Regional Input–Output tables to map the supply chain and to differentiate between the employment involved in the production of exported intermediate inputs and final goods. The results show that most of the employment involved in the production of final output of the activities studied in the paper is linked to international trade. Although Europe shows a high degree of productive links, there are important differences in the modality of insertion in the productive structure of European countries. Moreover, the impact on the level of employment due to the current economic crisis can be significant, affecting more than 1.3 million of people in Europe. These results are relevant to policy makers, who should consider carefully the high degree of linkages of the European economies when designing industrial policies and measure of support to the economy

Beyond equilibrium: revisiting two-sided markets from an agent-based modelling perspective

Two-sided markets are an important aspect of today's economies. Yet, the attention they have received in economic theory is limited, mainly due to methodological constraints of conventional approaches: Two-sided markets often exhibit non-trivial dynamics that are difficult to describe via analytical equilibrium models. We illustrate this point by revisiting a well-known equilibrium model of two-sided markets by Rochet and Tirole from an agent-based computational perspective. We identify several inconsistencies as well as implicit and implausible assumptions of the original model. These limit its explanatory power and motivate an alternative approach. The agent-based model we propose allows us to study two-sided markets in a more realistic and adequate manner: Not only are we able to compare different decision-making rules for the providers, we can also study situations with more than two providers. Thus, our model represents a first step towards a more realistic and policy-relevant study of two-sided markets

Beyond equilibrium: revisiting two-sided markets from an agent-based modelling perspective

Two-sided markets are an important aspect of today's economies. Yet, the attention they have received in economic theory is limited, mainly due to methodological constraints of conventional approaches: Two-sided markets often exhibit non-trivial dynamics that are difficult to describe via analytical equilibrium models. We illustrate this point by revisiting a well-known equilibrium model of two-sided markets by Rochet and Tirole from an agent-based computational perspective. We identify several inconsistencies as well as implicit and implausible assumptions of the original model. These limit its explanatory power and motivate an alternative approach. The agent-based model we propose allows us to study two-sided markets in a more realistic and adequate manner: Not only are we able to compare different decision-making rules for the providers, we can also study situations with more than two providers. Thus, our model represents a first step towards a more realistic and policy-relevant study of two-sided markets

Stage fever and text anxiety: the staging of poeticity in Dutch performance poetry since the 1960s

Over the past decades, the poetry performance has developed into an increasingly popular, diverse, and complex art form. In theoretical and critical discourse, it is referred to as performance poetry, spoken word poetry, and polipoesía; some theorists argue that it is an independent poetic genre, others treat it as a contemporary manifestation of oral poetry or of the poetry recital. The essays collected in this volume take up the challenge that the poetry performance poses to literary theory. Coming from a variety of disciplines, including Literary Studies, Theater Studies, and Area Studies, contributors develop new approaches and analytical categories for the poetry performance. They draw on case studies from a variety of contexts and in several languages, including Brazilian Portuguese, Dutch, Catalan, English, French, Galician, and Spanish. Essays are organized in three sections, which focus on critical and theoretical approaches to the poetry performance, on the mediatic hybridity of this art form, and on the ways in which the poetry performance negotiates locatedness through engagements with space and place. The structure of the volume intersperses essays on theory and analysis with self-reflexive essays from performance poets on their own performance practice

High and Low Protein∶ Carbohydrate Dietary Ratios during Gestation Alter Maternal-Fetal Cortisol Regulation in Pigs

Imbalanced maternal nutrition during gestation can cause alterations of the hypothalamic-pituitary-adrenal (HPA) system in offspring. The present study investigated the effects of maternal low- and high-protein diets during gestation in pigs on the maternal-fetal HPA regulation and expression of the glucocorticoid receptor (GR), mineralocorticoid receptor (MR), 11β-hydroxysteroid dehydrogenase 1 and 2 (11β-HSD1 and 11β-HSD2) and c-fos mRNAs in the placenta and fetal brain. Twenty-seven German Landrace sows were fed diets with high (HP, 30%), low (LP, 6.5%) or adequate (AP, 12.1%) protein levels made isoenergetic by varying the carbohydrate levels. On gestational day 94, fetuses were recovered under general anesthesia for the collection of blood, brain and placenta samples. The LP diet in sows increased salivary cortisol levels during gestation compared to the HP and AP sows and caused an increase of placental GR and c-fos mRNA expression. However, the diurnal rhythm of plasma cortisol was disturbed in both LP and HP sows. Total plasma cortisol concentrations in the umbilical cord vessels were elevated in fetuses from HP sows, whereas corticosteroid-binding globulin levels were decreased in LP fetuses. In the hypothalamus, LP fetuses displayed an enhanced mRNA expression of 11β-HSD1 and a reduced expression of c-fos. Additionally, the 11β-HSD2 mRNA expression was decreased in both LP and HP fetuses. The present results suggest that both low and high protein∶carbohydrate dietary ratios during gestation may alter the expression of genes encoding key determinants of glucocorticoid hormone action in the fetus with potential long-lasting consequences for stress adaptation and health

Effects of inadequate maternal dietary protein:carbohydrate ratios during pregnancy on offspring immunity in pigs

<p>Abstract</p> <p>Background</p> <p>Inadequate nutrition <it>in utero</it> may retard foetal growth and alter physiological development of offspring. This study investigated the effects of low and high protein diets fed to primiparous German Landrace sows throughout pregnancy on the immune function of their offspring at different ages. Sows were fed diets with adequate (AP, 12.1%; <it>n</it> = 13), low (LP, 6.5%; <it>n</it> = 15), or high (HP, 30%; <it>n</it> = 14) protein content, made isoenergetic by varying carbohydrate levels. Cortisol, total protein and immunoglobulin (IgG, IgM, IgA) concentrations were measured in the blood of sows over the course of pregnancy. Cortisol, total protein, immunoglobulins, lymphocyte proliferation, immune cell counts, and cytokines were assessed in the blood of offspring at baseline and under challenging conditions (weaning; lipopolysaccharide (LPS) administration).</p> <p>Results</p> <p>In sows, the LP diet increased cortisol (<it>P</it> < 0.05) and decreased protein levels (<it>P</it> < 0.01) at the end of pregnancy. Immunoglobulin concentrations were decreased in LP (IgA) and HP piglets (IgG, IgM and IgA) on the first day of life (<it>P</it> < 0.05), whereas the number of lymphocytes and mitogen-induced lymphocyte proliferation of the piglets were unaffected by the maternal diet. Mortality during the suckling period was higher in LP piglets compared with AP and HP offspring (<it>P</it> < 0.01). Furthermore, LP piglets showed an elevated cortisol response to weaning, and in HP piglets, the CD4⁺ cell percentage and the CD4⁺/CD8⁺ ratio increased after weaning (<it>P</it> < 0.05). The lipopolysaccharide-induced rise of IL-6 was higher in LP (<it>P</it> = 0.09) and HP (<it>P</it> < 0.01) compared with AP piglets, and LP piglets displayed higher IL-10 levels than AP piglets (<it>P</it> < 0.05).</p> <p>Conclusions</p> <p>Our results indicate that both low and high protein:carbohydrate ratios in the diet of pregnant sows can induce short-term as well as long-lasting effects on immune competence in piglets that may have serious consequences for host defence against bacterial pathogens.</p