Seeking theta's desperately: Estimating the distribution of consumers under increasing block rates

This paper shows that the distribution of observed consumption is not a good proxy for the distribution of heterogeneous consumers when the current tariff is an increasing block tariff. We use a two step method to recover the "true" distribution of consumers. First, we estimate the demand function induced by the current tariff. Second, using the demand system, we specify the distribution of consumers as a function of observed consumption to recover the true distribution. Finally, we design a new two-part tariff which allows us to evaluate the equity of the existence of an increasing block tariff.

Targeting fertility and female participation through the income tax

We evaluate the effect of a 2003 reform in the Spanish income tax on fertility and the employment of mothers with small children. The reform introduced a tax credit for working mothers with children under the age of three, while also increasing child deductions for all households with children. Theoretically, given the interplay of these two components, the expected effect of the reform is ambiguous on both outcomes. We find that the combined reforms significantly increased both fertility (by almost five percent) and the employment rate of mothers with children under three (by two percent). These effects were more pronounced among less-educated women. In addition, to disentangle the impact of the two reform components, we use an earlier reform that increased child deductions in 1999. We find that the child deductions affect mothers employment negatively, which implies that the 2003 tax credit would have increased employment even more (up to five percent) in the absence of the change in child deductions.

PyRate: a new program to estimate speciation and extinction rates from incomplete fossil data

Despite the advancement of phylogenetic methods to estimate speciation and extinction rates, their power can be limited under variable rates, in particular for clades with high extinction rates and small number of extant species. Fossil data can provide a powerful alternative source of information to investigate diversification processes. Here, we present PyRate, a computer program to estimate speciation and extinction rates and their temporal dynamics from fossil occurrence data. The rates are inferred in a Bayesian framework and are comparable to those estimated from phylogenetic trees. We describe how PyRate can be used to explore different models of diversification. In addition to the diversification rates, it provides estimates of the parameters of the preservation process (fossilization and sampling) and the times of speciation and extinction of each species in the data set. Moreover, we develop a new birth-death model to correlate the variation of speciation/extinction rates with changes of a continuous trait. Finally, we demonstrate the use of Bayes factors for model selection and show how the posterior estimates of a PyRate analysis can be used to generate calibration densities for Bayesian molecular clock analysis. PyRate is an open-source command-line Python program available at http://sourceforge.net/projects/pyrate/.

World population growth and fertility patterns, 1960-2000. A simple model explaining the evolution of world's fertility during the second half of the 20th Century

In this paper we attempt to describe the general reasons behind the world populationexplosion in the 20th century. The size of the population at the end of the century inquestion, deemed excessive by some, was a consequence of a dramatic improvementin life expectancies, attributable, in turn, to scientific innovation, the circulation ofinformation and economic growth. Nevertheless, fertility is a variable that plays acrucial role in differences in demographic growth. We identify infant mortality, femaleeducation levels and racial identity as important exogenous variables affecting fertility.It is estimated that in poor countries one additional year of primary schooling forwomen leads to 0.614 child less per couple on average (worldwide). While it may bepossible to identify a global tendency towards convergence in demographic trends,particular attention should be paid to the case of Africa, not only due to its differentdemographic patterns, but also because much of the continent's population has yet toexperience improvement in quality of life generally enjoyed across the rest of theplanet.

The effect of divorce laws on divorce rates in Europe

This paper analyzes a panel of 18 European countries spanning from 1950 to 2003 toexamine the extent to which the legal reforms leading to easier divorce that took placeduring the second half of the 20th century have contributed to the increase in divorce rates across Europe. We use a quasi-experimental set-up and exploit the different timing of the reforms in divorce laws across countries. We account for unobserved country-specificfactors by introducing country fixed effects, and we include country-specific trends tocontrol for time-varying factors at the country level that may be correlated with divorcerates and divorce laws, such as changing social norms or slow moving demographictrends. We find that the reforms were followed by significant increases in divorce rates.Overall, we estimate that the introduction of no-fault, unilateral divorce increased thedivorce rate by about 1, a sizeable effect given the average rate of 4.2 divorces per 1,000married people in 2002.

Speculative dynamics in the term structure of interest rates

When long maturity bonds are traded frequently and traders have non-nestedinformation sets, speculative behavior in the sense of Harrison and Kreps (1978) arises.Using a term structure model displaying such speculative behavior, this paper proposesa conceptually and observationally distinct new mechanism generating time varying predictableexcess returns. It is demonstrated that (i) dispersion of expectations about futureshort rates is sufficient for individual traders to systematically predict excess returns and(ii) the new term structure dynamics driven by speculative trade is orthogonal to publicinformation in real time, but (iii) can nevertheless be quantified using only publicly availableyield data. The model is estimated using monthly data on US short to medium termTreasuries from 1964 to 2007 and it provides a good fit of the data. Speculative dynamicsare found to be quantitatively important, potentially accounting for a substantial fractionof the variation of bond yields and appears to be more important at long maturities.

Labour market in the Catalan cotton textile sector: Employment and fertility (1850-1913)

This paper deals whit the dynamics of the Catalan textile labour market (theSpanish region that concentrated most of the industrial and factory activity duringthe 19 Century) and offers hypotheses and results on the impact it had on livingstandards and fertility levels. We observe the formation of an uneven labourmarket in which male supply for labour (excluding women and children) grewmuch faster than the demand. We stress the fact that labour supply is verydependant on institutional factors liked to the transmition of household propertybetween generations. Instead the slow path of growth of adult males demand forlabour is witnessing the limits of this industry to expand and to compete ininternational markets. The strategy of working class families to adapt to scarceopportunities of employment we document here is the diminution of legitimatefertility levels. Fertility control is the direct instrument we think workers have tocontrol their number in a situation that was likely to create labour surpluses in theshort and mid run.

Evolutionary rates of Jurassic ammonites in relation to sea-level fluctuations

An analysis is presented of the diversity and faunal turnover of Jurassic ammonites related to transgressive /regressive events. The data set contained 400 genera and 1548 species belonging to 67 ammonite zones covering the entire Jurassic System. These data were used in the construction of faunal turnover curves and ammonite diversities, that correlate with sea-level fluctuation curves. Twenty-four events of ammonite faunal turnover are analyzed throughout the Jurassic. The most important took place at the Sinemurian-Carixian boundary, latest Carixian-Middle Domerian, Domerian-Toarcian boundary, latest Middle Toarcian-Late Toarcian, Toarcian-Aalenian boundary, latest Aalenian-earliest Bajocian, latest Early Bajocian-earliest Late Bojocian, Early Bathonian-Middle Bathonian boundary, latest Middle Bathonian-earliest Late Bathonian, latest Bathonian-Early Callovian, earliest Early Oxfordian-Middle Oxfordian, earliest Late Oxfordian-latest Oxfordian, latest Early Kimmeridgian, Late Kimmeridgian, middle Early Tithonian and Early Tithonian-Late Tithonian boundary. More than 75 percent of these turnovers correlate with regressive-transgressive cycles in the Exxon, and /or Hallam's sea-level curves. Inmost cases the extinction events coincide with regressive intervals, whereas origination and radiation events are related to transgressive cycles. The turnovers frequently coincide with major or minor discontinuities in the Subbetic basin (Betic Cordillera).

Improving rainwater-use in Cabo Verde drylands by reducing runoff

Dryland agriculture in Cabo Verde copes with steep slopes, inadequate practices, irregular intense rain, recurrent droughts, high runoff rates, severe soil erosion and declining fertility, leading to the inefficient use of rainwater. Maize and beans occupy N80% of the arable land in low-input, low-yielding subsistence farming. Three collaborative field trialswere conducted in different agroecological zones to evaluate the effects ofwater-conservation techniques (mulching of crop residue, a soil surfactant and pigeon-pea hedges) combinedwith organic amendments (compost and animal or green manure) on runoff and soil loss. During the 2011 and 2012 rainy seasons, three treatments and one control (traditional practice) were applied to 44- and 24-m2 field plots. A local maize variety and two types of beanswere planted. Runoff and suspended sedimentswere collected and quantified after each daily erosive rainfall. Runoff occurred for rainfalls≥50mm(slope b10%, loamy Kastanozem),≥60mm(slope≤23%, silt–clay–loam Regosol) and≥40mm(slope≤37%, sandy loam Cambisol). Runoffwas significantly reduced only with themulch treatment on the slope N10% and in the treatment of surfactant with organic amendment on the slope b10%. Soil loss reached 16.6, 5.1, 6.6 and 0.4 Mg ha−1 on the Regosol (≤23% slope) for the control, surfactant, pigeon-pea and mulch/pigeon-pea (with organic amendment) treatments, respectively; 3.2, 0.9, 1.3 and 0.1 Mg ha−1 on the Cambisol (≤37% slope) and b0. 2Mg ha−1 for all treatments and control on the Kastanozem(b10% slope). Erosion was highly positively correlated with runoff. Mulch with pigeon-pea combinedwith an organic amendment significantly reduced runoff and erosion fromagricultural fields on steep slopes, contributing to improved use of rainwater at the plot level. Sustainable land management techniques, such as mulching with pigeon-pea hedges and an organic amendment, should be advocated and promoted for the semiarid hillsides of Cabo Verde prone to erosion to increase rainwater-use and to prevent further soil degradation.

Risk management under a two-factor model of the term structure of interest rates

This paper presents several applications to interest rate risk managementbased on a two-factor continuous-time model of the term structure of interestrates previously presented in Moreno (1996). This model assumes that defaultfree discount bond prices are determined by the time to maturity and twofactors, the long-term interest rate and the spread (difference between thelong-term rate and the short-term (instantaneous) riskless rate). Several newmeasures of ``generalized duration" are presented and applied in differentsituations in order to manage market risk and yield curve risk. By means ofthese measures, we are able to compute the hedging ratios that allows us toimmunize a bond portfolio by means of options on bonds. Focusing on thehedging problem, it is shown that these new measures allow us to immunize abond portfolio against changes (parallel and/or in the slope) in the yieldcurve. Finally, a proposal of solution of the limitations of conventionalduration by means of these new measures is presented and illustratednumerically.

A two-mean reverting-factor model of the term structure of interest rates

This paper presents a two--factor model of the term structure ofinterest rates. We assume that default free discount bond prices aredetermined by the time to maturity and two factors, the long--term interestrate and the spread (difference between the long--term rate and theshort--term (instantaneous) riskless rate). Assuming that both factorsfollow a joint Ornstein--Uhlenbeck process, a general bond pricing equationis derived. We obtain a closed--form expression for bond prices andexamine its implications for the term structure of interest rates. We alsoderive a closed--form solution for interest rate derivatives prices. Thisexpression is applied to price European options on discount bonds andmore complex types of options. Finally, empirical evidence of the model'sperformance is presented.

Malthusian dynamism and the rise of Europe: Make war, not love

This paper argues that Malthusian regimes are capable of sustained changes in per capita incomes. Shifting mortality and fertility schedules can lead to different steady-state income levels, with long periods of growth during the transition. Europe checked the downward pressure on wages through late marriage, which reduced fertility, and a mortality regime that combined high death rates with high incomes. We argue that both emerged as a result of the Black Death.

Fitness cost of resistance to Bacillus thuringiensis in velvetbean caterpillar Anticarsia gemmatalis Hübner (Lepidoptera, Noctuidae)

Selection pressure to obtain resistant genotypes can result in fitness cost. In this study, we report the effects of the selection pressure of a commercial formulation of Bacillus thuringiensis on biological aspects of a Dipel-resistant strain of velvetbean caterpillar, Anticarsia gemmatalis Hübner. Comparisons of Dipel-resistant and susceptible individuals revealed significant differences in pupal weight and larval development time. Both strains (Dipel-resistant and susceptible) were susceptible to Cry1Ac toxin expressed in foliar cotton tissues. Resistant and susceptible strains showed low survival rates of 22.5% and 51.2%, respectively, when fed with Greene diet containing Bt-cotton. Larvae bioassayed after three laboratory generations presented lower survival and less instar numbers than individuals maintained in the laboratory for more than 144 generations. Pupal weight was 9.4% lower and larval development time was 1.9 days longer in the resistant population than in the susceptible strain. Other parameters, such as duration of pupal stage, adult longevity, number of eggs per female, oviposition period, and egg fertility, remained unaffected.

The impact of women's educational and economic resources on fertility. Spanish birth cohorts 1901-1950

In this chapter we portray the effects of female education and professional achievementon fertility decline in Spain over the period 1920-1980 (birth cohorts of 1900-1950).A longitudinal econometric approach is used to test the hypothesis that the effectsof women s education in the revaluing of their time had a very significant influence onfertility decline. Although in the historical context presented here improvements inschooling were on a modest scale, they were continuous (with the interruption of theCivil War) and had a significant impact in shaping a model of low fertility in Spain. Wealso stress the relevance of this result in a context such as the Spanish for which liberalvalues were absent, fertility control practices were forbidden, and labour forceparticipation of women was politically and socially constrained.