Income dynamics and the life cycle

This paper argues that our understanding of income and poverty dynamics benefits from taking a life cycle perspective. A person¿s age and family circumstances ¿ the factors that shape their life cycle ¿ affect the likelihood of experiencing key life events, such as partnership formation, having children, or retirement; this in turn affects their probability of experiencing rising, falling, or other income trajectories. Using ten waves of the British Household Panel Survey, we analyse the income trajectories of people at different stages in their lives in order to build a picture of income dynamics over the whole life cycle. We find that particular life events are closely associated with either rising or falling trajectories, but that there is considerable heterogeneity in income trajectories following these different events. Typically, individuals experiencing one of these life events are around twice as likely to experience a particular income trajectory, but most individuals will not follow the trajectory most commonly associated with that life event. This work improves our understanding of the financial impact of different life events and provides an indication of how effectively the welfare state cushions people against the potentially adverse impact of certain events

Eastern Antarctic Peninsula precipitation delivery mechanisms: Process studies and back trajectory evaluation

Copyright @ 2008 Royal Meteorological SocietyThe atmospheric circulation patterns that result in precipitation events at a site on the eastern Antarctic Peninsula (AP) are investigated using back trajectories (BTs) driven by ERA-40 data. Moisture delivery occurs from the east and west depending on the location of blocking events in the South Atlantic and Pacific Oceans. Observations are sparse in this region, so our process studies compare the trajectories (and the ERA-40 fields from which they were derived) with advanced very high resolution radiometer (AVHRR) satellite images. It is found that the trajectories represent these transport mechanisms very well and that they are relatively insensitive to the initial trajectory elevation

Orbital motion effects in astrometric microlensing

We investigate lens orbital motion in astrometric microlensing and its detectability. In microlensing events, the light centroid shift in the source trajectory (the astrometric trajectory) falls off much more slowly than the light amplification as the source distance from the lens position increases. As a result, perturbations developed with time such as lens orbital motion can make considerable deviations in astrometric trajectories. The rotation of the source trajectory due to lens orbital motion produces a more detectable astrometric deviation because the astrometric cross-section is much larger than the photometric one. Among binary microlensing events with detectable astrometric trajectories, those with stellar-mass black holes have most likely detectable astrometric signatures of orbital motion. Detecting lens orbital motion in their astrometric trajectories helps to discover further secondary components around the primary even without any photometric binarity signature as well as resolve close/wide degeneracy. For these binary microlensing events, we evaluate the efficiency of detecting orbital motion in astrometric trajectories and photometric light curves by performing Monte Carlo simulation. We conclude that astrometric efficiency is 87.3 per cent whereas the photometric efficiency is 48.2 per cent.Comment: 9 pages, 8 figures, accepted for publication in MNRA

Income Dynamics and the Life Cycle

This paper argues that our understanding of income and poverty dynamics benefits from taking a life cycle perspective. A person¿s age and family circumstances ¿ the factors that shape their life cycle ¿ affect the likelihood of experiencing key life events, such as partnership formation, having children, or retirement; this in turn affects their probability of experiencing rising, falling, or other income trajectories. Using ten waves of the British Household Panel Survey, we analyse the income trajectories of people at different stages in their lives in order to build a picture of income dynamics over the whole life cycle. We find that particular life events are closely associated with either rising or falling trajectories, but that there is considerable heterogeneity in income trajectories following these different events. Typically, individuals experiencing one of these life events are around twice as likely to experience a particular income trajectory, but most individuals will not follow the trajectory most commonly associated with that life event. This work improves our understanding of the financial impact of different life events and provides an indication of how effectively the welfare state cushions people against the potentially adverse impact of certain events.income dynamics, life cycle, poverty

An examination of the precipitation delivery mechanisms for Dolleman Island, eastern Antarctic Peninsula

Copyright @ 2004 Wiley-BlackwellThe variability of size and source of significant precipitation events were studied at an Antarctic ice core drilling site: Dolleman Island (DI), located on the eastern coast of the Antarctic Peninsula. Significant precipitation events that occur at DI were temporally located in the European Centre for Medium-Range Weather Forecasting (ECMWF) reanalysis data set, ERA-40. The annual and summer precipitation totals from ERA-40 at DI both show significant increases over the reanalysis period. Three-dimensional backwards air parcel trajectories were then run for 5 d using the ECMWF ERA-15 wind fields. Cluster analyses were performed on two sets of these backwards trajectories: all days in the range 1979–1992 (the climatological time-scale) and a subset of days when a significant precipitation event occurred. The principal air mass sources and delivery mechanisms were found to be the Weddell Sea via lee cyclogenesis, the South Atlantic when there was a weak circumpolar trough (CPT) and the South Pacific when the CPT was deep. The occurrence of precipitation bearing air masses arriving via a strong CPT was found to have a significant correlation with the southern annular mode (SAM); however, the arrival of air masses from the same region over the climatological time-scale showed no such correlation. Despite the dominance in both groups of back trajectories of the westerly circulation around Antarctica, some other key patterns were identified. Most notably there was a higher frequency of lee cyclogenesis events in the significant precipitation trajectories compared to the climatological time-scale. There was also a tendency for precipitation trajectories to come from more northerly latitudes, mostly from 50–70°S. The El Niño Southern Oscillation (ENSO) was found to have a strong influence on the mechanism by which the precipitation was delivered; the frequency of occurrence of precipitation from the east (west) of DI increased during El Niño (La Niña) events

Conditional reversibility in nonequilibrium stochastic systems

For discrete-state stochastic systems obeying Markovian dynamics, we establish the counterpart of the conditional reversibility theorem obtained by Gallavotti for deterministic systems [Ann. de l'Institut Henri Poincar\'e (A) 70, 429 (1999)]. Our result states that stochastic trajectories conditioned on opposite values of entropy production are related by time reversal, in the long-time limit. In other words, the probability of observing a particular sequence of events, given a long trajectory with a specified entropy production rate $\sigma$, is the same as the probability of observing the time-reversed sequence of events, given a trajectory conditioned on the opposite entropy production, $-\sigma$, where both trajectories are sampled from the same underlying Markov process. To obtain our result, we use an equivalence between conditioned ("microcanonical") and biased ("canonical") ensembles of nonequilibrium trajectories. We provide an example to illustrate our findings.Comment: 13 pages, 1 figur