Hump-shaped Effect Research Articles

Information technology and lender competition

We study how information technology (IT) affects lender competition, entrepreneurs’ investment, and welfare in a spatial model. The effects of an IT improvement depend on whether it weakens the influence of lender–borrower distance on monitoring costs. If it does, it has a hump-shaped effect on entrepreneurs’ investment and social welfare. If not, competition intensity does not vary, improving lender profits, entrepreneurs’ investment, and social welfare. When entrepreneurs’ moral hazard problem is severe, IT-induced competition is more likely to reduce investment and welfare. We also find that lenders’ price discrimination is not welfare-optimal. Our results are consistent with received empirical work on lending to SMEs.

Comparing Seamounts and Coral Reefs with eDNA and BRUVS Reveals Oases and Refuges on Shallow Seamounts.

Seamounts are the least known ocean biome. Considered biodiversity hotspots, biomass oases, and refuges for megafauna, large gaps exist in their real diversity relative to other ecosystems like coral reefs. Using environmental DNA metabarcoding (eDNA) and baited video (BRUVS), we compared fish assemblages across five environments of different depths: coral reefs (15 m), shallow seamounts (50 m), continental slopes (150 m), intermediate seamounts (250 m), and deep seamounts (500 m). We modeled assemblages using 12 environmental variables and found depth to be the main driver of fish diversity and biomass, although other variables like human accessibility were important. Boosted Regression Trees (BRT) revealed a strong negative effect of depth on species richness, segregating coral reefs from deep-sea environments. Surprisingly, BRT showed a hump-shaped effect of depth on fish biomass, with significantly lower biomass on coral reefs than in shallowest deep-sea environments. Biomass of large predators like sharks was three times higher on shallow seamounts (50 m) than on coral reefs. The five studied environments showed quite distinct assemblages. However, species shared between coral reefs and deeper-sea environments were dominated by highly mobile large predators. Our results suggest that seamounts are no diversity hotspots for fish. However, we show that shallower seamounts form biomass oases and refuges for threatened megafauna, suggesting that priority should be given to their protection.

Birthplace diversity and team performance

Using hand-collected and web-scraped data on 7208 matches and 3266 players from the highest division of German male football, this paper examines how birthplace diversity affects team performance. The results of two instrumental variable analyses suggest that birthplace diversity has a hump-shaped effect on team performance. To explain our result, we argue that nationally diverse teams have a wider range of skills and face greater communication barriers.

Seed size affects rodent-seed interaction consistently across plant species but not within species: evidence from a seed tracking experiment of 41 tree species.

Scatter-hoarding rodents play a crucial role in seed survival and seed dispersal. As one of the most important seed traits, seed size and its effect on rodent-seed interaction attract lots of attention. Current studies usually target one or a few species and show inconsistent patterns; however, few experiments include a large number of species although many plant species usually coexist in natural forest and overlap in fruiting time. Here, we tracked the dispersal and predation of 26100 seeds belonging to 41 tree species in a subtropical forest for 2 years. Most species showed no relationships between seed size and rodent foraging preference, while the remaining species displayed diverse of patterns: monotonic decrease and increase trends, and hump-shaped and U-shaped patterns, indicating that a one-off study with a few species might give misleading information. However, the seed size effect across species was consistent in both years, indicating that including a large number of species that hold a sufficient range of seed size may avoid the aforementioned bias. Interestingly, seed size effect differed among rodent foraging processes: a negative effect on seed harvest, a hump-shaped effect on seed removal and removal distance, while a positive effect on overwinter survival of cached seeds, indicating that rodents may make trade-offs between large and small seeds both among foraging processes and within a single process, thus lead to a parabolic relationship between seed size and seed dispersal success, that is medium-sized seeds were more likely to be removed and cached, and transported with a further distance.

The hump-shaped effect of plant functional diversity on the biological control of a multi-species pest community

Plant taxonomic and functional diversity promotes interactions at higher trophic levels, but the contribution of functional diversity effects to multitrophic interactions and ecosystem functioning remains unclear. We investigated this relationship in a factorial field experiment comparing the effect of contrasting plant communities on parasitism rates in five herbivore species. We used a mechanistic trait-matching approach between plant and parasitoids to determine the amount of nectar available and accessible to parasitoids. This trait-matching approach best explained the rates of parasitism of each herbivorous species, confirming the predominant role of mass-ratio effects. We found evidence for an effect of functional diversity only in analyses considering the ability of plant communities to support the parasitism of all herbivores simultaneously. Multi-species parasitism was maximal at intermediate levels of functional diversity. Plant specific richness had a negligible influence relative to functional metrics. Plant communities providing large amounts of accessible nectar and with intermediate levels of functional diversity were found to be the most likely to enhance the conservation biological control of diverse crop herbivores.

Diversity of ants (Hymenoptera, Formicidae) along a heavy metal pollution gradient: Evidence of a hump-shaped effect

Abstract Ants, as indicators of ecological changes, are widely used in land management and environmental monitoring. At the same time, effects of industrial pollution are less known compared to many other stressors. We studied variations in habitat variables and ant diversity near the Karabash copper smelter (KCS) in Russia, in 2009 and 2014. Pitfall traps were set up at 10 birch forest sites (3 plots per site and 5 traps per plot) located to the north and south of the smelter within a 1–32-km range, with two samplings per season (June and August). The tree height, stand basal area, species richness of the field and moss layers, and the cover of the field layer decreased towards the smelter. The vegetation almost disappeared at the industrial barren close to KCS. In total, 21 ant species of 7 genera were registered. The highest species richness, diversity, and total occurrence of ants were observed in the transitional zone between moderately polluted forest habitats and industrial barren. Ant diversity and occurrence showed the same pattern in different years. Our results conform to the intermediate disturbance hypothesis predicting the greatest diversity at intermediate frequencies or intensities of disturbance or environmental change. Apparently, contaminant exposure affects ant communities near KCS indirectly, through habitat transformation. The study emphasizes the need for thorough planning of field studies of pollution effects on ants with examination of the full range of exposures. In addition, the nonlinear pattern of diversity and abundance of the ant community along the pollution gradients suggests caution, when assessing the magnitude of human impact and the state of ecosystems with ants as bioindicators.

Human genealogy reveals a selective advantage to moderate fecundity.

Life-history theory suggests that the level of fecundity of each organism reflects the effect of the trade-off between the quantity and quality of offspring on its long-run reproductive success. The present research provides evidence that moderate fecundity was conducive to long-run reproductive success in humans. Using a reconstructed genealogy for nearly half a million individuals in Quebec during the 1608-1800 period, the study establishes that, while high fecundity was associated with a larger number of children, perhaps paradoxically, moderate fecundity maximized the number of descendants after several generations. Moreover, the analysis further suggests that evolutionary forces decreased the level of fecundity in the population over this period, consistent with an additional finding that the level of fecundity that maximized long-run reproductive success was above the population mean. The research identifies several mechanisms that contributed to the importance of moderate fecundity for long-run reproductive success. It suggests that, while individuals with lower fecundity had fewer children, the observed hump-shaped effect of fecundity on long-run reproductive success reflects the beneficial effects of lower fecundity on various measures of child quality, such as marriageability and literacy, and thus on the reproductive success of each child.

Mortgage Usage and Mortgage Payments as Share of Income in China: Comparing Residential Homeowners and Housing Investors

The study investigates factors associated with mortgage usage and the share of income that Chinese use for mortgage payments. Using data from the 2010 China Family Panel Study, we found mortgage usage shows a hump-shaped income effect. Workers in government-controlled nonprofit institutions are more likely to use a mortgage to purchase a house because banks treat them favorably. Notably, government employees borrow less to purchase a residence because they have advantages by way of subsidies. Individuals who have attained higher education are more likely to use a mortgage and have a larger share of their monthly income devoted to mortgage payments. For housing investors, risk tolerance is positively associated with mortgage use but not with the share of mortgage payments in the household’s monthly expenditure.

Habitat preferences of breeding Yellow BuntingsEmberiza sulphuratain hilly rural areas following rice field abandonment in northern Japan

SummaryWe studied the habitat preferences of breeding Yellow BuntingsEmberiza sulphurata, taking into account the effects of paddyfield abandonment in hilly rural areas within the heavy snow region of northern Japan. Across 30 transects located in valley bottoms, we investigated the relationship between Yellow Bunting abundance and landscape characteristics. The results of generalized linear mixed models showed that forest edge density and landslide sites positively affected Yellow Bunting abundance. These habitats were associated with bush vegetation (forest edge, shrub land, and tall grassland) and were adjacent to the forest. Paddyfield abandonment showed a hump-shaped effect with a peak at the middle succession stage, which was covered primarily with tall grass and some shrubs, but the effect on Yellow Bunting abundance was not statistically significant. To conserve Yellow Bunting habitats in hilly rural areas, it is necessary to protect the forest edge and landslide sites from urbanisation and exploitation. It is also necessary to continue crop cultivation in such areas, to maintain the edges between open land and forest. If cultivation can no longer be continued, the abandoned paddyfields should be kept bushy, using reed beds and shrubs, by active management.

Climatic Fluctuations and the Diffusion of Agriculture.

This research examines the climatic origins of the diffusion of Neolithic agriculture across countries and archaeological sites. The theory suggests that a foraging society's history of climatic shocks shaped the timing of its adoption of farming. Specifically, as long as climatic disturbances did not lead to a collapse of the underlying resource base, the rate at which hunter-gatherers were climatically propelled to experiment with their habitats determined the accumulation of tacit knowledge complementary to farming. Consistent with the proposed hypothesis, the empirical investigation demonstrates that, conditional on biogeographic endowments, climatic volatility has a hump-shaped effect on the timing of the adoption of agriculture.

The Biocultural Origins of Human Capital Formation

This research explores the biocultural origins of human capital formation. It presents the first evidence that moderate fecundity and thus predisposition towards investment in child quality was conducive for long-run reproductive success within the human species. Using an extensive genealogical record for nearly half a million individuals in Quebec from the sixteenth to the eighteenth centuries, the study explores the effect of fecundity on the number of descendants of early inhabitants in the subsequent four generations. The research exploits variation in the random component of the time interval between the date of first marriage and the first birth to establish that while higher fecundity is associated with a larger number of children, an intermediate level maximizes long-run reproductive success. Moreover, the observed hump-shaped effect of fecundity on long-run reproductive success reflects the negative effect of higher fecundity on the quality of each child. The finding further indicates that the optimal level of fecundity was below the population median, lending credence to the hypothesis that during the Malthusian epoch, the forces of natural selection favored individuals with lower fecundity and thus larger predisposition towards child quality, contributing to human capital formation, the onset of the demographic transition and the evolution of societies from an epoch of stagnation to sustained economic growth.

Effects of intraspecific and community density on the lifetime fecundity of long-lived shrubs

Abstract Intra- and interspecific density dependence has profound consequences for plant population and community dynamics. In long-lived plants, however, lifetime patterns and mechanisms of density dependence are difficult to study. Here, we examine effects of intraspecific and community density on the lifetime fecundity of two long-lived shrub species from South African Fynbos: Protea repens (animal-pollinated, hermaphroditic) and Leucadendron rubrum (wind-pollinated, dioecious). Both species are serotinous, retaining seeds in cones until fire kills the mother plant. We measured lifetime fecundity as the product of cone number, proportion of cones that are not damaged by predation and seed set (fertile seeds per intact cone). Intraspecific and community densities were quantified by counting individuals of target species and all Proteaceae in small- and large-scale neighbourhoods (10 m and 50 m radius) around each focal individual. Additionally, we determined the age and size of focal individuals. We found that lifetime fecundity of the wind-pollinated L. rubrum is density independent. In contrast, the lifetime fecundity of the animal-pollinated P. repens increases with large-scale intraspecific density and shows a hump-shaped relationship to large-scale community density. Community density has a hump-shaped effect on seed set (probably through partial absence of generalized pollinators at low and competition for pollinators at high densities) and negatively affects cone number per individual. For both species, plant age decreases seed set while increasing lifetime fecundity. The qualitative differences in the density dependence of lifetime fecundity may arise from differences between animal and wind pollination. In particular, interactions with generalized animal pollinators may cause community-level Allee effects with profound consequences for the future dynamics of long-lived plant populations and communities.

The Productivity Effect of Temporary Agency Work: Evidence from German Panel Data

This study investigates the effect of temporary agency work on the user firm’s productivity. We hypothesise that using temporary agency work to enhance numerical flexibility and to screen job candidates may increase productivity, whereas temporary workers’ lower firm-specific human capital and spillover effects on the user’s permanent employees may adversely affect productivity. Other than the sparse existing literature on this issue, we exploit a large panel data set and control for time-invariant and time-varying unobserved heterogeneity by using the system GMM estimator. We find a robust hump-shaped effect of the extent of temporary agency work on the user firm’s productivity.

The 'Out of Africa' Hypothesis, Human Genetic Diversity, and Comparative Economic Development.

This research argues that deep-rooted factors, determined tens of thousands of years ago, had a significant effect on the course of economic development from the dawn of human civilization to the contemporary era. It advances and empirically establishes the hypothesis that, in the course of the exodus of Homo sapiens out of Africa, variation in migratory distance from the cradle of humankind to various settlements across the globe affected genetic diversity and has had a long-lasting effect on the pattern of comparative economic development that is not captured by geographical, institutional, and cultural factors. In particular, the level of genetic diversity within a society is found to have a hump-shaped effect on development outcomes in both the pre-colonial and the modern era, reflecting the trade-off between the beneficial and the detrimental effects of diversity on productivity. While the intermediate level of genetic diversity prevalent among Asian and European populations has been conducive for development, the high degree of diversity among African populations and the low degree of diversity among Native American populations have been a detrimental force in the development of these regions.

Intraspecific genotypic richness and relatedness predict the invasibility of microbial communities

Biological invasions can lead to extinction events in resident communities and compromise ecosystem functioning. We tested the effect of two widespread biodiversity measurements, genotypic richness and genotypic dissimilarity on community invasibility. We manipulated the genetic structure of bacterial communities (Pseudomonas fluorescens) and submitted them to invasion by Serratia liquefaciens. We show that the two diversity measures impact on invasibility via distinct and additive mechanisms. Genotypic dissimilarity of the resident communities linearly increased productivity and in parallel decreased invasion success, indicating that high dissimilarity prevents invasion through niche pre-emption. By contrast, genotypic richness exerted a hump-shaped effect on invasion and was linked to the production of toxins antagonistic to the invader. This effect peaked at intermediate richness, suggesting that high richness levels may increase invasibility. Invasibility could be well predicted by the combination of these two mechanisms, documenting that both genotypic richness and dissimilarity need to be considered, if we are to understand the biotic properties determining the susceptibility of ecosystems to biological invasions.

The 'Out of Africa' Hypothesis, Human Genetic Diversity, and Comparative Economic Development

This research argues that deep-rooted factors, determined tens of thousands of years ago, had a significant effect on the course of economic development from the dawn of human civilization to the contemporary era. It advances and empirically establishes the hypothesis that, in the course of the exodus of Homo sapiens out of Africa, variation in migratory distance from the cradle of humankind to various settlements across the globe affected genetic diversity and has had a long-lasting effect on the pattern of comparative economic development that is not captured by geographical, institutional, and cultural factors. In particular, the level of genetic diversity within a society is found to have a hump-shaped effect on development outcomes in both the pre-colonial and the modern era, reflecting the trade-off between the beneficial and the detrimental effects of diversity on productivity. While the intermediate level of genetic diversity prevalent among Asian and European populations has been conducive for development, the high degree of diversity among African populations and the low degree of diversity among Native American populations have been a detrimental force in the development of these regions.

China's Greenhouse Gas emissions’ dynamic effects in the process of its urbanization: A perspective from shocks decomposition under long-term constraints

Abstract This paper is about to quantify the effect of China's urbanization on greenhouse gas (GHG) emissions by separating the part driven by the economic growth from the whole effect. In order to be accurate to estimate unknown parameters, this paper follows the method of Blanchard & Quah (1989), in which identifying conditions are set by assuming some shocks have no long-term effect on corresponding explained variables. We conclude that 1) Urbanization shock has an inverted hump-shaped effect on GHG emissions, in other words, nowadays the process of China's urbanization has been accompanied with saving energy and reducing emissions; 2) The growth rate of GHG emissions, owning to the GDP shock, can be raised by almost 1.53% annually and the urbanization level approximately contributes to 18% of the change of CO2 emissions based on empirical results; 3) China's emission reductions, in the short run, are actualy in expense of decreasing economic growth and delaying the p rocess of its urbanization.

Exchange rate versus monetary aggregate targeting: the Turkish case

This article compares and contrasts the macroeconomic effects of exchange rate targeting and money supply targeting by using quarterly data from Turkey for the period February 1986–March 2000. The results of the VAR analysis show that the exchange rate does not have the traditional ‘hump-shaped effect’ that money supply has on output. In addition, we observe that an exchange rate depreciation leads to a temporary improvement in the trade balance for only a year, while monetary innovations have longer-lasting effects. Those results suggest that money-based targeting is more appropriate than exchange-rate targeting for Turkey.

Grazing intensity influences the strength of an associational refuge on temperate reefs

Recent studies have emphasized the role of positive interactions in ecological communities, but few have addressed how positive interactions are mediated by abiotic stress and biotic interactions. Here, I investigate the effect of a facilitator species on the abundance of macroalgae over a gradient of herbivory. Grazing by sea urchins can be intense on temperate reefs along the California coast, with benthic macroalgae growing exclusively in physical refuges and interspersed within colonies of the strawberry anemone, Corynactis californica. Field experiments indicated that the net effect of C. californica on turf algae was strongly nonlinear over a gradient in density of sea urchins. At low intensities of urchin grazing, the anemone and macroalgae competed for space, with algae capable of overgrowing C. californica. At intermediate grazing intensities, C. californica provided a refuge for turf algae but not for juvenile kelp. Neither turf algae nor kelp benefited from the presence of C. californica at the highest levels of grazing intensity, as sea urchins consumed nearly all macroalgae. The hump-shaped effect observed for C. californica contrasts with the prevailing view in ecological theory that positive interactions are more common in harsh environmental conditions. The results reported here qualify this view and underscore the need to evaluate positive interactions over a range of abiotic stress and consumer pressure.

When did unsystematic monetary policy have an effect on inflation?

An important stylized fact to emerge from VAR estimates is that exogenous monetary policy shocks (also labelled unsystematic monetary policy) have a delayed, persistent, hump-shaped effect on inflation. I argue that this empirical pattern is fragile. In particular, it disappears when one examines periods without large shifts in the level of inflation (such as 1984–2005). An important consequence is that the hump-shaped VAR estimated response of inflation is not appropriate to fit stylized models of the response of inflation around a stable steady state inflation level.