Estimates of the population by ethnic group for areas within England

This article describes, and provides some initial analysis of, the experimental population estimates by ethnic group for areas within England published by the Office for National Statistics (ONS) in January 2006. The article considers growth and the population structure of each of the ethnic groups identified in the 2001 Census; subnational patterns of change; population turnover; and measures of diversity and segregation, and also provides a comparison of the estimates and corresponding sample-based estimates from the Labour Force Survey.     

The development of a 'Postcode Best Fit' methodology for producing population estimates for different geographies

A 'Postcode Best Fit' methodology has been developed by the Office for National Statistics to produce population estimates for a range of different geographies which are entirely consistent with each other, regardless of whether or not the estimates for one geography can be aggregated to produce estimates for another geography. This article describes the Postcode Best Fit methodology, its evaluation, limitations with some of the data sources used with the method, the application of the method for producing population estimates and case studies describing how the method has been used to produce bespoke population estimates to meet specific user requirements.     

Methodology used for producing ONS's small area population estimates

The Office for National Statistics (ONS) has set up a project to investigate the feasibility of producing postcensal small area population estimates on a nationally consistent basis for England and Wales. Following on from earlier investigations to identify potential data sources and methods, ward and Super Output Area population estimates have been released as 'experimental statistics'. This article covers the methodology used to produce these estimates, feedback from user consultation with the initial estimates released at ward level, summary statistics on the population estimates for mid-2001 to mid-2003, and future developments for small area population estimates.     

Rebasing the annual mid-year population estimates for England and Wales

The ONS produces mid-year population estimates annually, which are based on updating from the most recent census. Therefore, whenever results become available from a census, a new base is created for the population estimates. This has implications for historic series, which need to be revised to be consistent with both the past and the most recent census. This article describes the methodology that will be used for this rebasing of the mid-year population estimates following the availability of results from the 2001 Census. Census results also provide a unique opportunity to assess the accuracy of the population estimates that are based on the previous census and this article also describes the approach that will be taken to the assessment of accuracy.     

Population estimates; backseries methodology for 1992-2000

In each decade, population estimates are rebased using data from the most recent census. However, this would lead to a step change in the population estimates series. To avoid this discontinuity the backseries for 1992 to 2000, was revised to bring it into line with the 2001 Census. This article discusses the methodology used to produce the final revised backseries for 1992 to 2000 published by ONS in October 2004. The final estimates were produced after a long period of research into the best methodology to use. Traditionally, the backseries have been revised using an interim simple period method, followed by a final simple cohort method. The approach taken following the 2001 Census was much more comprehensive. This article outlines this approach, summarises the range of methods available and describes in detail the final method selected.     

Reviewing the mid-year population estimates in Northern Ireland

This article describes the thorough review of the mid-year population estimates for Northern Ireland. No major problems have been identified with the current estimates but a number of enhancements have been put in place. The new figures are consistent with a number of administrative data sources. The overall effect has been to revise the estimated Northern Ireland population by about 6,000 people, or between 0.3 and 0.4 per cent, for each year between 1991 and 1997. The revised estimates for Northern Ireland have been incorporated into the population figures for the United Kingdom included in the Table section of this issue of Population Trends.     

An international comparative study on the use of the Cohort Component Method for estimating national populations

This comparative study explores the use of the Cohort Component Method (CCM) to produce national level population estimates. This method is used annually to calculate mid-year population estimates for England and Wales by the Office for National Statistics (ONS). Initially the article considers recent population change in England and Wales, with particular emphasis on the growing importance and challenges faced by migration estimation. Comparisons are then made between how population estimates are produced in England and Wales and other countries, with a particular focus on differences in the way the CCM is applied. Recent changes in methods used to estimate population are then reviewed along with a discussion of alternative approaches such as those described in academic literature.     

Stability and change in ethnic groups in England and Wales

The Office for National Statistics (ONS) Longitudinal Study (LS) is an exceptional resource for exploring dynamic processes in individuals' lives for a representative sample of the population of England and Wales and across a thirty year period, including how those processes vary by ethnic group. However, analyses tend to assume a certain stability in the meaning of the ethnic group being studied: the insights into ethnic group differentiation are premised on the fact that the group has the same meaning over time. Here we show how the LS allows us to challenge such notions of group stability. This has practical implications for the ways we measure and conceive of Britain's minority ethnic groups. We illustrate this point with two examples: one exploring the change in ethnic group identification by the same individuals between 1991 and 2001, and the second exploring how loss to follow up is differentially experienced according to ethnic group. We provide some suggestions on the implications of this ethnic group instability for other research.     

Projections of the population by ethnic group: a sufficiently interesting or a definitely necessary exercise to undertake?

This article considers the range of needs which would be met by having available projections of the population by ethnic group, and, in particular, the r?le these projections would usefully play in informing current and future policy issues. The article first identifies and lists the main uses, and potential users, of such projections and gives an appraisal of the likely applications in each context. Some of the challenges involved in using the main datasources--the census and surveys--for making such projections are then addressed; the article considers what is measured by asking questions on ethnicity, and discusses the implications of ethnicity being self-assessed--two important considerations which affect the potential usefulness of ethnic projections. Finally, details are given of a co-operative project involving a multi-disciplinary team of academic experts to explore the feasibility of making such projections.     

25 years of Population Trends

This article monitors some of the more significant demographic changes over the last twenty-five years, depicted in various issues of Population Trends. It is, of necessity, selective in coverage in terms of quotes, figures and topics. Other articles in this issue go into more depth on specific topics, such as families, ethnic minority groups, marriage and divorce, health inequalities and fertility and family planning. Consequently, there is some overlap and the articles could usefully be cross-referenced. Some coverage is also given to the development of sources, international events and selected partnerships outside the Office. Relevant legislation enacted over the period is also mentioned.     

The demographic situation in the European Union

This article is an update of a similar article published in Population Trends 104 and complements the article on European-wide issues in population statistics, published in Population Trends 118. The main areas of demography are covered, namely population change, population composition, fertility and mortality. Eurostat are currently working on a new set of population projections which should be available shortly, but were not completed when this article was drafted.     

Short-term international migration trends in England and Wales from 2004 to 2009

Short-term migration estimates for England and Wales are the latest addition to the Office for National Statistics (ONS) migration statistics. This article discusses definitions of short-term migration and the methodology that is used to produce the estimates. Some of the estimates and the changes in the estimates over time are then discussed. The article includes previously unpublished short-term migration statistics and therefore helps to give a more complete picture of the size and characteristics of short-term international migration for England and Wales than has previously been possible. ONS have identified a clear user requirement for short-term migration estimates at local authority (LA) level. Consequently, attention is also paid to the progress that has been made and future work that is planned to distribute England and Wales short-term migration estimates to LA level.     

How have administrative sources been used to adjust population estimates and set plausibility ranges?

This article reviews existing methods employed by various countries in the use of administrative data to make adjustments to, or set plausibility ranges around, population estimates or census data. The work was carried out to explore techniques that could be used by the ONS in application with population estimates. An annex also covers benefits and difficulties that have been experienced when producing a register-based census, or population estimates.     

理性群体决策的概率集结研究

探讨如何集结多个专家的不确定性信息,以获得群体一致判断．首先分析群体理性存在的可能性;在此基础上,给出了几种集结个体概率的模型及算式,讨论了这些模型的特点,实际应用的可能性;最后,评述了Ｄａｌｋｅｙ个体概率集结不可能性定理中潜在的问题。得出几个研究的结论,并且提出了需要进一步研究的问题。     

A comparison of official population projections with Bayesian time series forecasts for England and Wales

We compare official population projections with Bayesian time series forecasts for England and Wales. The Bayesian approach allows the integration of uncertainty in the data, models and model parameters in a coherent and consistent manner. Bayesian methodology for time-series forecasting is introduced, including autoregressive (AR) and stochastic volatility (SV) models. These models are then fitted to a historical time series of data from 1841 to 2007 and used to predict future population totals to 2033. These results are compared to the most recent projections produced by the Office for National Statistics. Sensitivity analyses are then performed to test the effect of changes in the prior uncertainty for a single parameter. Finally, in-sample forecasts are compared with actual population and previous official projections. The article ends with some conclusions and recommendations for future work.     

The use of patient registers to estimate migration

This article presents information discussed at the recent regional seminars on population statistics. It describes a new data source for estimating internal migration between local and health authorities in England and Wales, discusses the way that the data have been collected and processed, and how limitations in the raw data have been addressed. It then goes on to explain the way that the new internal migration estimates have been used in the calculation of population estimates for local and health authorities. This is a change to the method of estimating migration in the calculation of population estimates.     

基于CTMC族的多部件装备群稳态可用度建模方法

针对复杂可修装备群稳态可用度解析计算困难的问题,提出一种通过构建多个相关连续时间马尔可夫链(continuous time Markov chain,CTMC)来求解稳态可用度的方法。通过分析装备群的使用与维修特点,采用可用装备数、备件库存数、备件短缺数来刻画部件的状态,分别建立各类部件库存状态的CTMC,进而建立用于分析装备群稳态可用度的CTMC族模型;并根据各类部件的状态转移关系及转移率矩阵,在求解各类部件CTMC模型稳态概率的基础上,给出各类部件的期望备件短缺数和装备群稳态可用度算法。最后通过构建数值案例,将提出的CTMC族模型结果分别与仿真分析和多级可修产品库存控制模型的结果进行对比,验证了提出模型和算法的有效性。     

ANP 内部独立循环系统超矩阵构造的改进方法

在网络分析(ANP)中,如何科学合理地构造出被评价问题的超矩阵是一个非常重要的技术关键.针对内部独立循环型系统(CSII)问题,ANP在超矩阵的一个重要子矩阵即方案对目标的影响矩阵(IMAG)构造时采用了和其它子矩阵完全相同的构造方式,即点估计方式.这种构造方式并没有合理反映IMAG构造的整体论思想,实质即整体性逻辑判断的高度不确定性特征.为克服上述缺陷,建议专家采用区间估计而非点估计的方式来反映其相对偏好的判断.为了使这种理论观点能够在实际评价中得以实施,通过建立数据包络分析模型,提出了一种CSII型系统超矩阵的改进构造方法.具体例子应用结果表明,该方法是科学可靠的,对内部独立循环系统的排序问题有着很强的实际应用可操作性.     

基于主元分析和免疫聚类的双向特征数据压缩方法

针对诊断特征数据中的重复或相似事例样本和特征参量之间可能存在的相关性，提出并实现了一种有效的特征数据双向压缩预处理方法，从而在不损失数据隐含的特征知识的前提下，有效降低学习机器的学习负担。在进行样本参量的降维处理时，采用基于主元分析的横向数据压缩方法，有效地去除了各特征参量之间的相关性。在压缩样本数量时，综述和比较了现有的各种聚类算法，基于竞争和自组织原理，对借鉴生物体的自然免疫系统中克隆选择以及免疫网络自稳定等有关机理的常规免疫聚类压缩算法，作了重要改进，提出了基于主元核相似度的亲和力定义方法，增加了抗原数据归一化、近似样本直接去除等处理步骤，使算法具有更高的执行效率和更广的适应性。并以国际上通用的过程控制仿真对象“Tennessee Bastman”工厂的实际数据进行仿真实验，验证了所提方法的有效性。     

THE POPULATION DYNAMICS WITH N-INTERSECTIONS

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