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 The article includes previously unpublished short-term migration statistics and therefore helps to give a more complete picture of the size and characteristics of short-term international migration for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.     

Using administrative data sources in the estimation of emigration

It is important that migration is measured accurately, for example to inform population estimates and projections. However, current sources of information present challenges in producing robust estimates of emigration from Great Britain. This article reports on work carried out by the Office for National Statistics to investigate the potential for using administrative data sources to contribute to the measurement of emigration.     

The feasibility of making short-term migration estimates

Short-term migration, that is stays of less than 12 months, has received particular attention recently from both national and local level users of population statistics. This interest is part of the wider interest shown in increasing levels of long-term migration statistics in recent years. This article is an initial assessment by ONS of the potential to produce short-term migration estimates for England and Wales, and the challenges faced in doing so. Central to these challenges is the question of how short-term migration should be defined. In addition, illustrative estimates of short-term migration based on the International Passenger Survey (IPS) are provided. These illustrative estimates, along with associated standard errors, are provided at both national and regional levels using a number of definitional bases.     

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.     

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.     

Fifty years of United Kingdom national population projections: how accurate have they been?

This article considers the accuracy of the official national population projections made for the UK over the last fifty years The findings take account of the revision to population estimates following the 2001 Census and are largely similar to the findings of a previous review carried out after the 1991 Census. The total population has been projected reasonably accurately but this is largely a chance result of compensating errors in the assumptions of fertility, mortality and net migration. The largest differences between projected and actual populations are for the very young and the very old, while projections of the working age population have been comparatively accurate. Fertility and mortality errors have reduced in more recent projections, while migration errors have grown. However, this may simply reflect the volatility or stability of the respective time-series at the time the projections are made. Changes in estimates of the past and current size of the population (highlighted by the revisions made to population estimates following the 2001 Census) are also shown to play a part in explaining projection error.     

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.     

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.     

Using the Omnibus Survey to test questions on emigration

It is important that migration is measured accurately, for example to inform population estimates and projections. However, current sources of information make it difficult to produce robust estimates of emigration from Great Britain. Several other countries, including Ireland, make use of household surveys in their estimates of migration. To investigate the feasibility of obtaining information on emigration from those resident in Great Britain, three questions were included in the Omnibus Survey for two months. Respondents were asked whether they had plans to emigrate or whether anyone in their family had recently emigrated or intended to shortly. This article reports on the results of this pilot, providing evidence on response levels, comparison with the International Passenger Survey and feedback from interviewers on the questions asked.     

Small area population estimates project: data quality of administrative datasets

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. Research has taken place to identify datasets that could potentially be used within a method to produce small area population estimates. Following an evaluation of a number of different administrative datasets, the most suitable have been short-listed for further consideration. This article presents the findings of the evaluation, based on 2001 data, and summarises the characteristics of these short-listed data sources. This article does not cover the methods that are being evaluated as part of the feasibility assessment.     

Migration trends at older ages in England and Wales

Information on the behaviour and characteristics of our rapidly growing older population is of increasing importance to policy makers, who want to ensure a good quality of life for our elderly. This article uses data from the Office for National Statistics Longitudinal Study (1971-2001) to illustrate trends in migration at older ages. It shows how the propensity to migrate differs by age, sex, marital status, living arrangements, economic resources and health in later life, amongst people aged 50 and over in England and Wales. Results show that moves at older ages are associated with changes in health and living arrangements, but also that these associations are inter-related with other factors such as age.     

应用自适应时频分布的瞬时频率估计

估计信号的瞬时频率常用解析信号的相位差分或Cohen类时频分布的时间一阶条件矩 ,但这些方法在信噪比较低时存在较大的方差。提出了一种新的瞬时频率估计方法 ,它把被分析的信号自适应地扩展到一组有限的 ,具有较好的时频局部化特征的基函数集上 ,用相应的自适应时频分布的谱峰检测来估计信号瞬时频率。仿真结果表明 ,该方法具有较好的抗噪声能力 ,且能够灵活地应用于估计多分量信号的瞬时频率 ,可以取得比其它方法更好的效果。     

基于HKKP估计的商业银行操作风险估计

对于商业银行而言，操作风险已经成为与市场风险和信用风险同样重要的风险。本文利用极值理论对中国商业银行操作损失极端值分布进行估计，针对尾参数估计的采用传统Hill估计对小样本数据容易产生偏倚的情况，提出了采用Hill估计的改进——小样本无偏估计的HKKP估计来估计操作损失的尾参数，针对由于阈值确定不准确导致结果偏差大的情况，采用最小化估计的累计概率分布与经验累计概率分布平均平方误差的方法确定较精确的阈值，估计出给定置信水平下操作风险损失的分位数，从而使得中国商业银行操作风险监管资本的测定成为可能。     

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.     

基于三维CT数据的放射治疗剂量计算

研究和实现了一种基于医学序列CT图像的放射治疗蒙特卡罗剂量计算方法。通过改写蒙特卡罗剂量计算软件DPM(doseplanningmethod),使其具有处理三维CT图像数据的能力,其中CT值的组织物理参数标定采用一种新的神经网络的简化方法,并得到了可视化的剂量计算结果。探索了在实际临床肿瘤放疗计划中用DPM进行精确快速剂量计算的路径。实验结果证明了算法的正确性、有效性,对于提高放射治疗水平和精确放疗的后续研究具有一定的指导意义。     

Estimating the changing population of the 'oldest old'

The population of England and Wales is becoming older. This poses an increasing demand for detailed data on the size an trends of the population at the oldes ages. Using the recently released Offic for National Statistics estimates of th population aged 90 and over in England and Wales, this article shows trends in the population of the oldest old and demographic causes of the rapid increase in centenarians during the twentieth century. It also presents further validation of the ON estimates of the oldest old with estimat from other data sources.     

卡尔曼滤波在非寿险未决赔款准备金估算中的应用

在历史数据缺乏和数据质量较低的情况下,非寿险公司应用传统的准备金估计方法常存在估计精度不高的问题.本文通过状态空间来描述非寿险赔付过程,应用卡尔曼滤波来估计状态空间的转换参数,并分别预测损失频率和损失程度从而动态地估计未决赔款准备金.实证分析表明,在历史数据较少争存在错误数据的情况下,本方法对改善未决赔款准备金的估计是有效的.     

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.