Indirect effects of an aid program: how do liquidity injections affect non-eligibles' consumption?

Aid programs in developing countries are likely to affect both the treated and the non-treated households living in the targeted areas. Studies that focus on the treatment effecton the treated may fail to capture important spillover effects. We exploit the unique designof an aid program's experimental trial to identify its indirect effect on consumption for non-eligible households living in treated areas. We find that this effect is positive, and that itoccurs through changes in the insurance and credit markets: non-eligible households receivemore transfers, and borrow more when hit by a negative idiosyncratic shock, because of theprogram liquidity injection; thus they can reduce their precautionary savings. We also testfor general equilibrium effects in the local labor and goods markets; we find no significantchanges in labor income and prices, while there is a reduction in earnings from sales ofagricultural products, which are now consumed rather than sold. We show that this classof aid programs has important positive externalities; thus their overall effect is larger thanthe effect on the treated. Our results confirm that a key identifying assumption - that thetreatment has no effect on the non-treated - is likely to be violated in similar policy designs. Aid programs in developing countries are likely to affect both the treated and the non-treated households living in the targeted areas. Studies that focus on the treatment effecton the treated may fail to capture important spillover effects. We exploit the unique designof an aid program's experimental trial to identify its indirect effect on consumption for non-eligible households living in treated areas. We find that this effect is positive, and that itoccurs through changes in the insurance and credit markets: non-eligible households receivemore transfers, and borrow more when hit by a negative idiosyncratic shock, because of theprogram liquidity injection; thus they can reduce their precautionary savings. We also testfor general equilibrium effects in the local labor and goods markets; we find no significantchanges in labor income and prices, while there is a reduction in earnings from sales ofagricultural products, which are now consumed rather than sold. We show that this classof aid programs has important positive externalities; thus their overall effect is larger thanthe effect on the treated. Our results confirm that a key identifying assumption - that thetreatment has no effect on the non-treated - is likely to be violated in similar policy designs

DINAMICA DI VEGETAZIONE IN AREE DI POST-ABBANDONO DELLA PIANURA PADANA

VEGETATION DYNAMICS IN ABANDONED FIELDS IN THE PO PLAIN (ITALY) Human impact and the mechanization of agricultural activitities have deeply modified the natural landscape in the Po plain (northern Italy), as well as in other countries. Forest vegetation in this area has strongly declined since the Neolithic (CASTELLETTI E ROTTOLI, 1998), with subsequent modifications of forest structure and floristic composition. Nonetheless, the recent decrease of agricultural pressure has enhanced the development of postcultural vegetation dynamics, allowing us to start an examination the vegetation dynamics in the Po plain. In order to identify the dynamic series of the Po plain area, we have analyzed the secondary vegetation dynamics in sample abandoned fields of the upper plain of Milan and Lecco and woody communities of the Gera D\u2019Adda neighbourhood (Bergamo) which, in dynamical terms, represents the final stage of the series. The first case-study concerns the area of Rio Vallone Plis (Milan), which measures 1181 hectares and is located in the Pleistocene and Holocene alluvial sediments of the upper Po plain. The chronosequence or space-for-time substitution approach (PICKETT, 1989; FOSTER & TILMAN 2000) was applied to examine the temporal changes in vegetation. The method included the collocation of relev\ue9s in sites of different \u2013preferably known\u2013 age at given time intervals, assuming that the samples would represent the distinct stages of a temporal series. The historical study was realized by comparing orthocorrected aerial photographs taken in different years (1954, 1980, 1998, 2003, and 2006). Fifty-six relev\ue9s were made by using the phytosociological approach (BRAUN \u2013 BLANQUET, 1932; WESTHOFF & VAN DER MAAREL, 1973). Two matrices (relev\ue9s/species, Landolt ecological index average values/cluster) were constructed from the resulting data set, in order to analyse the relationships between ecological variables and the different clusters of vegetation. Matrices were processed separately through a multivariate analysis approach (PCA) using the SYN-TAX 5.0 software (PODANI, 1995). The third matrice (relev\ue9s/life forms) was processed in order to analyse the relationships between life forms abundance and the age stage of the studied sites, through ANOVA analysis with the SPSS 10.0 software and later analysis by means of Pearson a 2-code correlation. Nomenclature of taxa, corological elements and life forms follow PIGNATTI (1997) and AESCHIMANN & AL (2004). Two main series of secondary succession were distinguished according to their environmental and soil conditions: (a) the acidophylous series of middle Pleistocene terrace (Mindel Auct.) develops from the first herbaceous nitrophylous stage, belonging either to Chenopodion glauci (igrophylous variant) or Dauco-Picridetum hieracioidis (mesoxerophylous variant), to a second herbaceous-shrubland stage, which can be referred to either to Convolvulo-Eupatorietum cannabini (igrophylous variant) or Convolvuletalia sepium (mesoxerophylous variant), to a third forest-edge stage that can be attributed to shrubland communities Prunetalia spinosae, and eventually to the last stage, which is represented by wood referable to Quercetalia robori petraeae. The regressive stage is identified by the communities of Prunus serotina; (b) the mesophylous series of Holocene terrace develops from the first nitrophylous herbaceous stage belonging to Arrhenatheretalia elatioris, to a second forest-edge stage referable to shrubland communities (Sambuco-robinieti) referable to Carpinion betuli, and to the final stage made up mesophylous oak-hornbeam wood attributed to Carpinion betuli. The regressive stage belongs to communities referred to Prunetalia spinosae The second case study regards the phytosociological definition of the mesophylous and mesoigrophylous oak-hornbeam forests set on late Pleistocene and Holocene alluvial sediments of the upper Po plain, in the Gera d\u2019Adda (Bergamo). Thirty-one relev\ue9s were performed by using the phytosociological approach (BRAUN \u2013 BLANQUET, 1932; WESTHOFF & VAN DER MAAREL, 1973). Two matrices were processed separately through a multivariate analysis approach (PCA) with the SYN-TAX 5.0 software (PODANI, 1994). The results indicate that clusters are distributed according to three main ecological gradients (defined by the LANDOLT index): soil moisture value (F); soil pH value (R); soil aeration value (D). The historical study, which was realized by comparing historical maps of different years (1833, 1889) with recent regional topographic maps (CTR, 1991), shows that Orfano Wood has relict characteristic. Orfano Wood is referred to two different associations: (a) Querco-Ulmetum Issler 1926 for the igrophylous communities on Holocene sediments; (b) Polygonato multiflori \u2013Quercetum roboris subass. carpinetosum betuli Sartori 1980, which was included by ANDREIS e SARTORI (2002) in the Alnion incanae Pawlowski et Pawlowski et Wallisch 1928 (Alno-Ulmion minoris Br.-Bl. Et Tx.43), for the mesophylous communities developed on Holocene sediments. Concerning the other wood located on the Pleistocene \u201cmain level of the Po plain\u201d, the mesophylous woods belongs to Erythronio-Carpinion alliance (Hovart 1958) Marin\u10dek in Walln\uf6fer et al. 1993, with igrophylous variant referable to Alnion incanae Pawlowski et Pawlowski et Wallisch 1928 alliance (Alno-Ulmion minoris Br.-Bl. Et Tx.43)

Village economies and the structure of extended family networks

This paper documents how the structure of extended family networks in rural Mexico relates to the poverty and inequality of the village of residence. Using the Hispanic naming convention, we construct within-village extended family networks in 504 poor rural villages. Family networks are larger (both in the number of members and as a share of the village population) and out-migration is lower the poorer and the less unequal the village of residence. Our results are consistent with the extended family being a source of informal insurance to its members

Family networks and school enrolment: evidence from a randomized social experiment

We present evidence on whether and how a household’s behavior is influenced by the presence and characteristics of its extended family. Using data from the PROGRESA program in Mexico, we exploit information on the paternal and maternal surnames of heads and spouses in conjunction with the Spanish naming convention to identify the inter and intra generational family links of each household to others in the same village. We then exploit the randomized research design of the PROGRESA evaluation data to identify whether the treatment effects of PROGRESA transfers on secondary school enrolment vary according to the characteristics of extended family. We find PROGRESA only raises secondary enrolment among households that are embedded in a family network. Eligible but isolated households do not respond. The mechanism through which the extended family influences household schooling choices is the redistribution of resources within the family network from eligibles that receive de facto unconditional cash transfers from PROGRESA, towards eligibles on the margin of enrolling children into secondary school

Effective lattice actions for correlated electrons

We present an exact, unconstrained representation of the electron operators in terms of operators of opposite statistics. We propose a path--integral representation for the $t$-$J$ model and introduce a parameter controlling the semiclassical behaviour. We extend the functional approach to the Hubbard model and show that the mean--field theory is equivalent to considering, at Hamiltonian level, the Falikov--Kimball model. Connections with a bond-charge model are also discussed.Comment: 12 pages, REVTeX 3.0, no figure

Evaluation of optimal lateral resisting systems for tall buildings subject to horizontal loads

The tendency of modern designs towards optimal structures often leads to the lightest and best performing choice among a large set of design alternatives. In a similar scenario, the introduction of automated tools to further guide designers in achieving efficient solutions has been a recurrent topic for mechanical and structural engineers, over the past decades. Nowadays, topology optimization is considered a powerful preliminary design tool to determine the optimal material distribution in a design domain, i.e. the most effective configuration that satisfies a given set of prescribed constraints while reducing the consumption of structural material. Among different applications in the field of Civil Engineering, this work focuses on the definition of optimal layouts of lateral resisting systems for multi-storey steel building frameworks subject to lateral loads using topology optimization techniques. The objective of the research is to illustrate the benefits deriving from the introduction of automated routines within the preliminary design stage and establish reliable guidelines for performing accurate and objective optimization procedures. Since the optimal material distribution follows the load flow within the structure, optimal topologies are especially sensitive to the alteration of support and loading conditions: different loading scenarios naturally lead to distinct optimal layouts. In order to avoid the loss of objectivity and preserve the optimality of the results, the effects that preliminary modelling and loading assumptions produce on final layouts are investigated. Numerical applications to high-rise building models are presented and discussed

A new modular structural system for tall buildings based on tetrahedral configuration

Inspired by the high mechanical performance of diagrid structures, the minimization of material consumption on braced tubes and the expressive potency of tensegrity modular structures, this work proposes an innovative three-dimensional system for tall buildings. A new modular structural system generated from the assembly of tetrahedral units is investigated. The paper integrates insights on the architectural implications and mechanical performance of the reticular system arranged in repetitive triangular-based modules. The impact of different geometric configurations of the structural members on the economic design is also discussed and recommendations for the optimal topology are made. Guidelines for the design and analytical formula for accessing preliminary member sizes are proposed on the basis of stiffness requirements

Quantification of energy-related parameters for near-fault pulse-like seismic ground motions

An energy-based approach facilitates the explicit consideration of the damage associated with both maximum displacements and cumulative plastic deformations under earthquakes. For structural systems that can undergo pulse-like seismic ground motions close to causative faults, an energy-based approach is deemed especially appropriate with respect to well-established force-or displacement-based strategies. In such a case, in fact, most of the damage is attributable to the dominant pulse-like component, which usually occurs into the velocity time history of the seismic ground motion, thus implying high energy levels imparted to a structural system. In order to enable the implementation of an energy-based approach in the analysis and design of structures under near-fault pulse-like seismic ground motions, this study presents a comprehensive numerical investigation about the influence of seismological parameters and hysteretic behavior on the spectra of the following energy-related parameters: inelastic absolute and relative input energy; input energy reduction factor; hysteretic energy dissipation demand; hysteretic energy reduction factor; dimensionless cumulative plastic deformation ratio. Closed-form approximations are proposed for these spectra, and the numerical values of the corresponding parameters have been also calibrated (with reference to both mean and standard deviation values) as functions of earthquake magnitude, type of hysteretic behavior (i.e., non-degrading or degrading) and ductility level. The outcomes of this study are meant to support the derivation of design spectra for the energy-based seismic design of structures under near-fault pulse-like seismic ground motions

Consumption and Investment in Resource Pooling Family Networks

This paper examines a novel motive for resource pooling in family networks in rural economies: to relax credit constraints and facilitate investment in non-collateralizeable assets for which credit market imperfections are most binding. We thus complement established literatures examining risk-sharing motives for resource transfers within family networks, as well as motives based on kinship tax obligations. We do so exploiting the Progresa program data, in which family networks can be identified, households are subject to large exogenous resource inflows, and detailed responses on consumption and an array of investments can be tracked in a household panel over five years. We find that for every dollar that accrues to the family network through Progresa transfers, food consumption expenditures increase by around 65c/ for both households eligible for Progresa and ineligible members of the same family network. Hence the marginal propensity of families to invest/save out of every dollar is around .35, and we document how this is channelled towards easing credit constraints poorer network members face in financing non-collateralizable investments into their children's human capital. We show these consumption and investment benefits of being embedded within a family network are sustained five years after households first experience resource transfers from Progresa. Hence the interplay between resource inflows and resource pooling by family networks can place network members on sustained paths out of poverty