Household Saving Behaviour in New Zealand: A Cohort Analysis

This paper seeks to improve our understanding of household saving behaviour. It is based on an analysis of unit record data from March years 1984 to 1998 taken from the Household Economic Survey (HES). There are limitations of the data set but it provides the only available estimates of income and expenditure, from which saving is estimated as a residual. The HES is a series of cross-sectional surveys rather than a true panel, so we construct synthetic cohorts rather than tracking individual households. We use a range of regression models to separate out the effect of age, birth-year cohort and year on saving rates. The typical age profile for savings is hump-shaped, peaks around age 57 and does not become negative at older ages. Such a profile appears to have shifted down for the cohorts born between 1920 and 1939 relative to the younger and older cohorts studied. This pattern of cohort effects is robust to the inclusion of conditioning variables and to the trimming from the sample of households with either negative or very large ratios of savings to consumption. Preliminary investigation supports the hypothesis that changes in the economic and policy environment help explain the different saving behaviour of different birth cohorts. Tentative results suggest that more favourable environments are associated with lower rates of lifetime saving, although more research is needed to confirm this finding.Household saving, lifecycle, age, cohorts

Household Saving Behaviour in New Zealand: Why do Cohorts Behave Differently?

The aim of this paper is to add to the understanding of saving decisions by households. The saving behaviour of households is found to differ depending on the birth cohort of the household head. This paper seeks to explain why this pattern might exist. It is based on an analysis of synthetic cohorts derived from unit record data taken from the Household Economic Survey (HES) for the March years 1984 to 1998. The need to use synthetic cohorts arises as the HES is not a longitudinal panel survey, but rather a time series of independent cross-sectional samples. We use a range of regression models to separate out the effect of age, birth-year cohort and year on saving rates. The typical saving rates for the cohorts born between 1920 and 1939 are found to be significantly lower relative to the younger and older cohorts studied. This pattern of cohort effects is robust to the inclusion of conditioning variables; to the trimming from the sample of households with either negative or very large ratios of savings to consumption, and to different definitions of saving. Some exploratory investigation supports the hypothesis that changes in the economic and policy environment help explain the different saving behaviour of different birth cohorts. Tentative results suggest that more ?favourable environments are associated with lower rates of lifetime saving.Household saving rates; cohort effects; New Zealand; economic and social policies

Gas Phase Hydrolysis and Oxo-Exchange of Actinide Dioxide Cations: Elucidating Intrinsic Chemistry from Protactinium to Einsteinium.

Gas-phase bimolecular reactions of metal cations with water provide insights into intrinsic characteristics of hydrolysis. For the actinide dioxide cations, actinyl(V) AnO2 + , melding of experiment and computation provides insights into trends for hydrolysis, as well as for oxo-exchange between actinyls and water that proceeds by a hydrolysis pathway. Here this line of inquiry is further extended into the actinide series with CCSD(T) computations of potential energy surfaces, for the reaction pathway for oxo-exchange through hydrolysis of nine actinyl(V) ions, from PaO2 + to EsO2 + . The computed surfaces are in accord with previous experimental results for oxo-exchange, and furthermore predict spontaneous exchange for CmO2 + , BkO2 + , CfO2 + and EsO2 + , but not for AmO2 + . Natural Bond Order analysis of the species involved in both hydrolysis and oxo-exchange reveals an inverse correlation between the barrier to hydrolysis and the charge on the actinide centre, q(An). Based on this correlation, it can be concluded that hydrolysis, and related phenomena such as oxo-exchange, become less favourable as the charge on the metal centre decreases. The new results provide a straightforward rationalization of trends across a wide swathe of the actinide series

Carbon-sulfur bond strength in methanesulfinate and benzenesulfinate ligands directs decomposition of Np(v) and Pu(v) coordination complexes.

Gas-phase coordination complexes of actinyl(v) cations, AnO2+, provide a basis to assess fundamental aspects of actinide chemistry. Electrospray ionization of solutions containing an actinyl cation and sulfonate anion CH3SO2- or C6H5SO2- generated complexes [(AnVO2)(CH3SO2)2]- or [(AnVO2)(C6H5SO2)2]- where An = Np or Pu. Collision induced dissociation resulted in C-S bond cleavage for methanesulfinate to yield [(AnVO2)(CH3SO2)(SO2)]-, whereas hydrolytic ligand elimination occurred for benzenesulfinate to yield [(AnVO2)(C6H5SO2)(OH)]-. These different fragmentation pathways are attributed to a stronger C6H5-SO2-versus CH3-SO2- bond, which was confirmed for both the bare and coordinating sulfinate anions by energies computed using a relativistic multireference perturbative approach (XMS-CASPT2 with spin-orbit coupling). The results demonstrate shutting off a ligand fragmentation channel by increasing the strength of a particular bond, here a sulfinate C-S bond. The [(AnVO2)(CH3SO2)(SO2)]- complexes produced by CID spontaneously react with O2 to eliminate SO2, yielding [(AnO2)(CH3SO2)(O2)]-, a process previously reported for An = U and found here for An = Np and Pu. Computations confirm that the O2/SO2 displacement reactions should be exothermic or thermoneutral for all three An, as was experimentally established. The computations furthermore reveal that the products are superoxides [(AnVO2)(CH3SO2)(O2)]- for An = Np and Pu, but peroxide [(UVIO2)(CH3SO2)(O2)]-. Distinctive reduction of O2- to O22- concomitant with oxidation of U(v) to U(vi) reflects the relatively higher stability of hexavalent uranium versus neptunium and plutonium

CO2 conversion to phenyl isocyanates by uranium(vi) bis(imido) complexes.

Uranium(vi) trans-bis(imido) complexes [U(κ4-{(tBu2ArO)2Me2-cyclam})(NPh)(NPhR)] react with CO2 to eliminate phenyl isocyanates and afford uranium(vi) trans-[O[double bond, length as m-dash]U[double bond, length as m-dash]NR]2+ complexes, including [U(κ4-{(tBu2ArO)2Me2-cyclam})(NPh)(O)] that was crystallographically characterized. DFT studies indicate that the reaction proceeds by endergonic formation of a cycloaddition intermediate; the secondary reaction to form a dioxo uranyl complex is both thermodynamically and kinetically hindered

Gas-Phase Complexes of Americium and Lanthanides with a Bis-triazinyl Pyridine: Reactivity and Bonding of Archetypes for F-Element Separations.

Bis-triazinyl pyridines (BTPs) exhibit solution selectivity for trivalent americium over lanthanides (Ln), the origins of which remain uncertain. Here, electrospray ionization was used to generate gas-phase complexes [ML3]3+, where M = La, Lu, or Am and L is EtBTP 2,6-bis(5,6-diethyl-1,2,4-triazin-3-yl)-pyridine. Collision-induced dissociation (CID) of [ML3]3+ in the presence of H2O yielded a protonated ligand [L(H)]+ and hydroxide [ML2(OH)]2+ or hydrate [ML(L-H)(H2O)]2+, where (L-H)- is a deprotonated ligand. Although solution affinities indicate stronger binding of BTPs toward Am3+ versus Ln3+, the observed CID process is contrastingly more facile for M = Am versus Ln. To understand the disparity, density functional theory was employed to compute potential energy surfaces for two possible CID processes, for M = La and Am. In accordance with the CID results, both the rate determining transition state barrier and the net energy are lower for [AmL3]3+ versus [LaL3]3+ and for both product isomers, [ML2(OH)]2+ and [ML(L-H)(H2O)]2+. More facile removal of a ligand from [AmL3]3+ by CID does not necessarily contradict stronger Am3+-L binding, as inferred from solution behavior. In particular, the formation of new bonds in the products can distort kinetics and thermodynamics expected for simple bond cleavage reactions. In addition to correctly predicting the seemingly anomalous CID behavior, the computational results indicate greater participation of Am 5f versus La 4f orbitals in metal-ligand bonding

Activation of Water by Pentavalent Actinide Dioxide Cations: Characteristic Curium Revealed by a Reactivity Turn after Americium.

Swapping of an oxygen atom of water with that of a pentavalent actinide dioxide cation, AnO2+ also called an "actinyl", requires activation of an An-O bond. It was previously found that such oxo exchange in the gas phase occurs for the first two actinyls, PaO2+ and UO2+, but not the next two, NpO2+ and PuO2+. The An-O bond dissociation energies (BDEs) decrease from PaO2+ to PuO2+, such that the observation of a parallel decrease in the An-O bond reactivity is intriguing. To elucidate oxo exchange, we here extend experimental studies to AmO2+, americyl(V), and CmO2+, curyl(V), which were produced in remarkable abundance by electrospray ionization of Am3+ and Cm3+ solutions. Like other AnO2+, americyl(V) and curyl(V) adsorb up to four H2O molecules to form tetrahydrates AnO2(H2O)4+ with the actinide hexacoordinated by oxygen atoms. It was found that AmO2+ does not oxo-exchange, whereas CmO2+ does, establishing a "turn" to increasing the reactivity from americyl to curyl, which validates computational predictions. Because oxo exchange occurs via conversion of an actinyl(V) hydrate, AnO2(H2O)+, to an actinide(V) hydroxide, AnO(OH)2+, it reflects the propensity for actinyl(V) hydrolysis: PaO2+ hydrolyzes and oxo-exchanges most easily, despite the fact that it has the highest BDE of all AnO2+. A reexamination of the computational results for actinyl(V) oxo exchange reveals distinctive properties and chemistry of curyl(V) species, particularly CmO(OH)2+

The Enrichment History of Hot Gas in Poor Galaxy Groups

We have analyzed the ASCA SIS and GIS data for seventeen groups and determined the average temperature and abundance of the hot x-ray emitting gas. For groups with gas temperatures less than 1.5 keV we find that the abundance is correlated with the gas temperature and luminosity. We have also determined the abundance of the alpha-elements and iron independently for those groups with sufficient counts. We find that for the cool groups (i.e. kT <1.5 keV) the ratio of alpha-elements to iron is ~1, about half that seen in clusters. Spectral fits with the S, Si and Fe abundances allowed to vary separately suggest the S/Fe ratio is similar to that seen in clusters while the Si/Fe ratio in groups is half the value determined for richer systems. The mass of metals per unit blue luminosity drops rapidly in groups as the temperature drops. There are two possible explanations for this decrease. One is that the star formation in groups is very different from that in rich clusters. The other explanation is that groups lose much of their enriched material via winds during the early evolution of ellipticals. If the latter is true, we find that poor groups will have contributed significantly (roughly 1/3 of the metals) to the enrichment of the intergalactic medium.Comment: 19 Pages with 2 figures, Accepted for publication in the Astrophysical Journa