Econometric flexibility in microsimulation: an age-centred regression approach

This paper describes a strategy for estimating predictive equations that has been shown to work well in microsimulation modelling. The technique, referred to here as ?age-centred regression,? is particularly useful when the available data set for estimating a model equation is limited and the marginal effect of one or more explanatory variables might be expected to vary systematically by age. The examples used here to describe how age-centring works are taken from the labour supply equations in the Congressional Budget Office Long-Term (CBOLT) dynamic microsimulation model. By switching from a traditional single-equation approach to age-centred regression, we show that marginal effects of independent variables can vary significantly across age groups. The comparison also reveals that improvements in mean predictions by age can be achieved with little if any loss in statistical precision of coefficient estimates.age-centred regression; heterogeneity; spline; kernel

Perspectives on the Household Saving Rate

macroeconomics, household saving rate

Understanding the postwar decline in United States saving: a cohort analysis

An analysis of the postwar decline in U.S. national saving that decomposes changes in the net national saving rate into those due to changes in cohort-specific consumption propensities, the intergenerational distribution of resources, the rate of government spending, and demographics. ; A review and expansion of Calomiris, Kahn, and Longhofer's (1994) cultural affinity theory of discrimination in the residential mortgage market, which is based on the idea that lenders find it easier or less costly to evaluate the creditworthiness of applicants with whom they have a common experiential background.Saving and investment

The Flight Telerobotic Servicer (FTS) NASA's first operational robotic system

NASA has completed the preliminary definition phase of the Flight Telerobotic Servicer (FTS) and is now preparing to begin the detailed design and fabrication phase. The FTS will be designed and built by Martin Marietta Astronautics Group in Denver, CO, for the Goddard Space Flight Center, in support of the Space Station Freedom Program. The design concepts for the FTS are discussed, as well as operational scenarios for the assembly, maintenance, servicing and inspection tasks which are being considered for the FTS. The upcoming Development Test Flight (DTF-1) is the first of two shuttle test flights to test FTS operations in the environment of space and to demonstrate the FTS capabilities in performing tasks for Space Station Freedom. Operational planning for DTF-1 is discussed as well as development plans for the operational support of the FTS on the space station

Microscopic surface structure of C/SiC composite mirrors for space cryogenic telescopes

We report on the microscopic surface structure of carbon-fiber-reinforced silicon carbide (C/SiC) composite mirrors that have been improved for the Space Infrared Telescope for Cosmology and Astrophysics (SPICA) and other cooled telescopes. The C/SiC composite consists of carbon fiber, silicon carbide, and residual silicon. Specific microscopic structures are found on the surface of the bare C/SiC mirrors after polishing. These structures are considered to be caused by the different hardness of those materials. The roughness obtained for the bare mirrors is 20 nm rms for flat surfaces and 100 nm rms for curved surfaces. It was confirmed that a SiSiC slurry coating is effective in reducing the roughness to 2 nm rms. The scattering properties of the mirrors were measured at room temperature and also at 95 K. No significant change was found in the scattering properties through cooling, which suggests that the microscopic surface structure is stable with changes in temperature down to cryogenic values. The C/SiC mirror with the SiSiC slurry coating is a promising candidate for the SPICA telescope.Comment: 25 pages, 6 figure

Wealth Inequality and Retirement Preparedness: A Cross-Cohort Perspective

High and rising US wealth inequality underscores the need to revisit a perennial concern in policy circles: retirement preparedness. Our cross-cohort approach to studying retirement adequacy is based on relative wealth measures, meaning how the wealth distribution of one cohort compares to the cohorts ahead of them at the same age. We introduce relative rank distributions that show where individuals are in terms of the cohorts ahead of them at the same age, and percentile point comparisons that show how wealth levels at various percentiles vary across cohorts by age. We find that early Baby Boomer’s wealth is generally on par with or above 1930s cohort wealth at age 60. There is, however, evidence of relative wealth declines in the bottom of the wealth distribution for mid-late Boomers and Gen-Xers relative to earlier cohorts at younger ages, which is consistent with rising wealth inequality across and within generations. Social security is an important offset to relative wealth declines at the bottom of the wealth distribution, but those benefits are not expected to be fully payable for the youngest cohorts

The annuitization of Americans' resources: a cohort analysis

An analysis of the changes since 1960 in the share of Americans' resources that are annuitized, which has declined slightly for younger Americans but has risen dramatically for the elderly, with important implications for the national saving rate and income inequality.Saving and investment

Fahrspur- und Routenplanung für teilautonome, GNSS-gestützte Landmaschinen

Die Entwicklungen in der Landwirtschaft sind durch Automatisierung und Informationstechnologie geprägt. Parallelfahrsysteme sind zu einem wichtigen Werkzeug geworden, um die Maschine mit einer Spurgenauigkeit von wenigen Zentimetern auf dem Feld zu navigieren. Die vorliegende Arbeit beschreibt ein Planungsprogramm, mit dem ein automatisches Lenksystem zu einem teilautonomen Feldroboter ohne Mehrmaschinenkooperationen weiterentwickelt wurde. Hierfür sind fünf notwendige Planungsschritte konzipiert worden. Im ersten Schritt werden die notwendigen Eingabeparameter Feldgrenze und Hindernisse aufgezeichnet und nachbearbeitet, die notwendigen Maschinenparameter wurden ebenfalls in das System eingegeben. Das Feld wird in Bereiche unterteilt und Bearbeitungsrichtungen für die Teilbereiche bestimmt. Die Fahrspuren werden mithilfe der eingegebenen Daten flächendeckend generiert und Wendeflächen vorgesehen. Im Anschluss wird eine Teilfeld- sowie Fahrspurreihenfolge mittels Methoden des Operations Research berechnet. Es wird gezeigt, dass die verwendeten Algorithmen für eine Feldteilung, Auswahl einer Abarbeitungsrichtung und für eine Spurerstellung die Arbeitszeit um durchschnittlich 5 % minimieren können. Ein Modell zur Arbeitszeitabschätzung für ein gegebenes Feld wird gebildet und verifiziert. Das Sequenzieren der Teilfelder und Fahrspuren wird ebenfalls durch das Programm vorgeplant. Durch eine solche Fahrstrategieplanung wird die Wendezeit um ca. 50 % verringert. Ein weiterer wichtiger Baustein für das System ist die Überwachung. Neben den Neuberechnungen der Routen aufgrund von situationsbedingten, von den Landwirten angestoßenen Planänderungen werden auch Wendemanöver geplant und ausgeführt. Teilautonome Landmaschinen sind in einer Forschungsphase und haben aufgrund der Menge an noch zu lösenden Entwicklungsaufgaben die Marktreife nicht erreicht. In dieser Arbeit wird ein Assistenzsystem und kein autonomer, mobiler Roboter vorgestellt. Es werden Vorschläge für jeden Planungsschritt generiert und diese - nach Bestätigung oder Änderung durch den Anwender - ausgeführt. Der Vorteil ist somit, dass jeder automatisch generierte Schritt manuell geändert werden kann. Das System ist modular aufgebaut und Erweiterungen des Systems sind möglich, sodass auch andere nicht betrachtete Feldprozesse teilautonom gefahren werden können. Alle Algorithmen sind auf einen minimalen Rechenzeitbedarf ausgelegt. Analysen bestätigen die Anwendbarkeit auf einem Maschinenterminal.Path and route planning for semi-autonomous, GNSS-based agricultural machinery The presented work shows a strategy how semi-autonomous driving on the field can be realised. The focus is on the application in an agricultural vehicle with integration of a GNSS guidance system and its functionalities. Weather and situation dependent driving routes and limited computational resources during field process result in an important requirement of a planning system, an agile and fast recomputation. Further savings were realised by computer-aided optimisation algorithms. The system has a modular structure and it is shown how it can be extended for planning steps with special restrictions. The field process is modeled based on machine data, thus working time and route length can be estimated. With recorded real data, the model is verified. The working time minimisation is implemented by defined cost function. New algorithms for field division and track generation can save up to 5 percent working time. Also the track order was optimised, so that the turning time can be reduced up to 50 percent. In addition, also recomputation because of plan deviation was implemented. The software scope contained a method to generate turning manoeuvres so that the connection of two field tracks can be computed with the shortest possible path length drivable for GNSS steering systems. Semi-autonomous agricultural machines based on a GNSS steering system are still in focus of research and predevelopment phases developed. In this work, an assistance system and not an autonomous, mobile robot is presented. There are proposals for each planning step generated and - after confirmation or amendment by the user - executed. The advantage is that any auto-generated step can be changed manually. A general modular system is designed. Extensions are possible so that further not considered field processes can be operated semi-autonomously. For several processes, such as combine harvesting, the machine-utilisation shall be optimised. This thesis deals with working time minimisation, while Multi-machine communication was not subject of the thesis

Investigation of the NOAA N' S Search and Rescue Antenna Inadvertent Deployment: Type C Mishap

The NOAA N' Search and Rescue Antenna (SRA) inadvertently deployed during a spacecraft rotation on April 14,2007. This rotation was part of a normal operation to configure the spacecraft for additional antenna and the solar array boom deployments. This procedure (red flag written) had been modified to look for a lost metal washer and a thermal blanket button. The modification to the procedure was reviewed and approved by the Lockheed Martin Missiles and Space (LMMS) Material Review Board (MRB) per standard procedures. The flag to the procedure introduced a counter clockwise rotation before the normal clockwise rotation. The antenna was temporally stowed and held in place via lacing cord. The lacing cord broke and allowed the SRA to inadvertently deploy during the clockwise rotation. The SRA broke through a hard stop bracket and damaged an instrument optical sensor radiator panel. The satellite damage appears to be minimal and there were no injuries to personnel. The damage to the Advanced Microwave Sounding Unit (AMSU)-A1 instrument has not been fully assessed. Based on mishap site visits, interviews and data analysis, the Mishap Investigation Team (MIT) identified the underlying causes of the mishap. Event and causal factor tree diagrams were developed, resulting in the identification of the proximate (or direct) cause and root causes of the mishap