Wildlife census methods: a resume.
Wildlife census problems and sampling schemes are discussed. Basic census methods are presented. Examples of inventory techniques utilized for various wildlife species are mentioned.
Animals↗
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The abridged census method as an estimator of lifetime risk.
The abridged census estimator, also known as Weinberg's shorter method, is a device used to estimate lifetime incidence from the observed age distribution of a population at risk coupled with data on the current prevalence of a mental disorder. This method, which still enjoys considerable popularity, should have been replaced many years ago by more accurate techniques for making such estimates using similar information. In particular, the abridged census method uses the assumption that the remaining life expectancy of incident cases equals that of non-cases. This assumption is likely to lead to an underestimate of the lifetime risk. Two examples are presented from published literature which illustrate some problems encountered with the use of the abridged census method. Some alternative estimation methods are presented which can be implemented using only a hand calculator and which lead to more accurate results.
Alzheimer Disease↗
The Demeny-Shorter and three-census methods for correcting age data.
This paper presents, tests, applies, and compares methods that utilize age data collected at consecutive censuses to examine and adjust for age and coverage errors. The Demeny-Shorter method, for example, was devised for this purpose, and its flexibility in regard to census coverage errors is examined. The Demeny-Shorter method is found difficult to apply directly, so a method based on the same idea as the Demeny-Shorter method but utilizing age data from three, instead of two, successive censuses is presented and discussed as a possible alternative. This three-census method is applied to data from Turkey's censuses and, in some cases, found to be better than the Demeny-Shorter method, because the former allows for and estimates the likely changes in census coverage and different patterns of age errors in successive censuses. Unfortunately, the three-census method cannot be applied to data from most developing countries on account of a lack of the requisite series of censuses.
Demography↗
Highly reliable genetic identification of individual northern hairy-nosed wombats from single remotely collected hairs: a feasible censusing method.
The highly endangered northern hairy-nosed wombat (Lasiorhinus krefftii) is extremely difficult to study in the wild, and its numbers correspondingly difficult to estimate. Disturbance to the animals caused by trapping and radio-tracking may not only constitute an excessive risk to the population's viability, but may also yield biased data. The results of a pilot study are presented, which clearly show noninvasive genotyping to be a highly feasible and reliable alternative censusing method for L. krefftii. The protocol can identify individual wombats from single hairs collected remotely at burrow entrances, using: (i) a panel of microsatellite markers giving individual-specific genotypes; and (ii) a Y-linked sexing marker in combination with a single-copy X-linked amplification control. Using just the eight most variable microsatellites (of 20 available), only one in 200 pairs of full-sibs are predicted to share the same genotype. From 12 wombat hair samples collected on tape suspended over burrow entrances, three known female, two known male and an unknown wombat of each sex were identified. The approach will allow censusing of individuals that evade capture, and will also reveal some otherwise problematic aspects of the behaviour of this elusive animal.
Animals↗
Diurnal primate densities and biomass in the Kakamega Forest: an evaluation of census methods and a comparison with other forests.
Line-transect surveys were conducted at the Isecheno study site in the Kakamega Forest, western Kenya to estimate diurnal primate densities. The estimates from several different methods of analysis of census data were compared to "true" density values based on home range size and overlap for two species. The Whitesides method [Whitesides et al., 1988], which incorporates species-specific mean group spread into its formula for estimating transect width, provided the most accurate density estimates. The importance of including as many groups as possible when calculating density from home range size and overlap is demonstrated with long-term data from Colobus guereza and Cercopithecus mitis. Colobus guereza group density at Isecheno was much lower than that published from a recent brief study [von Hippel, 1996]. Cercopithecus mitis group density has fallen while overall population biomass appears to have remained stable over 20 years of study. Isecheno has the second highest diurnal primate biomass of the ten Guineo-Congolian rainforest sites for which biomass data are available, despite having the lowest primate species richness. Within the Guineo-Congolian rainforest system, primate biomass appears to vary to some extent between ecogeographic regions: two of three mid-elevation East African sites have high biomasses, two of two lowland West African sites have intermediate biomasses, and four of five lowland Central African sites have low biomasses. There is a strong positive correlation between total colobine biomass and total primate biomass at the ten Guineo-Congolian rainforest sites.
Animals↗
[Choice of heart surgery patients by the medical census method].
Cardiosurgical patients were selected in Novosibirsk during medical census of persons suffering from valvular disease; 2244 (81.2%) patients with congenital valvular diseases and 3979 (51.5%) those with acquired valvular diseases were chosen for operative treatment. Among patients with congenital valvular diseases, 12.1% underwent operation, surgery was indicated in 32.5%, and a follow-up of the pathological process was recommended in 36.6% of patients. In the group of acquired valvular diseases, 7.0% of patients were operated on, operation was indicated in 27.6%, and a follow-up recommended in 51.5% of patients.
Cardiac Surgical Procedures↗
The population dynamics and fertility of the trio of surinam: an application of a two census method.
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Adolescent↗
Application of a capture-recapture method (the Bernoulli census) to historical epidemiology.
Obstacles to historical epidemiologic research are formidable, especially for periods prior to the 19th century. Linguistic and paleographic difficulties are compounded by haphazard contemporary documentation and subsequent archival wastage, making real variations in disease frequency difficult to distinguish from record loss. This report investigates the application of a capture-recapture model, adapted from work on mobile animal populations, to this problem or archival loss. With the use of this technique, the original size of a psychiatric case population is estimated from incomplete extant enumerations. The cases are derived fron the Court of Wards and Liveries (1540-1660), the first statutory institution in England responsible for protecting persons legally incompetent due to mental disability. Documentation on this population survives in at least 10 record collections, the most extensive containing at best 82% of all original cases, the least extensive, 1%. Calculations based on extant files indicate a fourfold increase in the incidence of mental disability certifications between 1540-1549 and 1630-1639. The results of applying the Bernoulli census method to these materials eliminate biased archival loss as a plausible explanation for this rise. The origin of these changes in altered court policy or procedure, population growth, or increasing rates of mental disability awaits further investigation. While the Bernoulli census computations with historical data are mathematically equivalent ot those employed in recent epidemiologic applications, this specific data set prompts a conceptual revision of the Bernoulli model from capture to loss of random samples.
Animals↗
New method to census primate groups: estimating group density of Japanese macaques by point census.
We devised a new method to estimate the density of primate groups in habitats that preclude the use of a line-transect census because the ground is too steep. We combined point census and group follows. From the number of groups counted at a fixed point for an hour, n, group density D was calculated: D = lambda n / pi. Lambda, the detectability constant, was a constant when distance-dependent detectability g(y) was regressed on a half-normal model: g(y) = e (-lambda y(2)) and can be estimated by combining the information of group follow and point census. Using this method, we estimated the group density of Japanese macaques in Yakushima. A census area of 7 km(2) was divided into 28 grid squares (500 m x 500 m). One observer was positioned at a point in each grid square, and those points were censused simultaneously for 4-6 days from 0600-0700 to 1500-1600 hr. Four troops were followed for 144 hr during the point census. Distance-dependent detectability closely correlated with the half-normal model. The detectability constant varied with the time of day, but it was not influenced by troop identity or topography. Group density was calculated to be 1.48 +/- 0.61 and 0.701 +/- 0.432 groups/km(2) in the disturbed and undisturbed areas, respectively (95% confidence limit). "True" group density estimated by home range data was within the confidence limit calculated by a point census in the home range of the troops for two troops, suggesting that this method was valid. This method is applicable to other species as long as at least one group can be followed, because it satisfies the fundamental assumptions of point census, and the detectability does not seem to be biased by troop or topography.
Animals↗
Every death counts: measurement of maternal mortality via a census.
Methods for measuring maternal mortality at national and subnational levels in the developing world lag far behind the demand for estimates. We evaluated use of the national population census as a means of measuring maternal mortality by assessing data from five countries (Benin, Islamic Republic of Iran, Lao People's Democratic Republic, Madagascar, and Zimbabwe) which identified maternal deaths in their censuses. Standard demographic methods were used to evaluate the completeness of reporting of adult female deaths and births in the year prior to the census. The results from these exercises were used to adjust the data. In four countries, the numbers of adult female deaths needed to be increased and three countries required upward adjustment of the numbers of recent births. The number of maternal deaths was increased by the same factor as that used for adult female deaths on the assumption that the proportion of adult female deaths due to maternal causes was correct. Age patterns of the various maternal mortality indicators were plausible and consistent with external sources of data for other populations. Our data suggest that under favourable conditions a national census is a feasible and promising approach for the measurement of maternal mortality. Moreover, use of the census circumvents several of the weaknesses of methods currently in use. However, it should also be noted that careful evaluation of the data and adjustment, if necessary, are essential. The public health community is urged to encourage governments to learn from the experience of these five countries and to place maternal mortality estimation in the hands of statistical agencies.
Censuses↗
Computer methods in population census data processing.
"The paper summarises the findings of an international survey of census processing methods used in the 1990 round. Extensive use is made of computers, although the technologies involved vary considerably from country to country. There is more extensive discussion of the use made of computer-assisted and automatic coding, non-keyboard data entry methods and the establishment of population databases." The geographical scope is worldwide. (SUMMARY IN FRE)
Censuses↗
A parametric method for census based estimation of child mortality.
"A parametric method for estimating child mortality from reports concerning children ever born and surviving children is presented. In contrast with previously proposed methods, it facilitates use of single-year age reports by mothers on the survival of their children. In addition, the new method makes it possible to incorporate a priori knowledge of child mortality and fertility in the estimation process. The new method is illustrated by means of an application to data from the 1976 Western Samoa census."
Age Factors↗
Evaluating census data quality using intensive reinterviews: a comparison of U.S. Census Bureau methods and Rasch methods.
"In this paper, we consider Rasch measurement methodology as an alternative to conventional U.S. Census Bureau methodology for evaluating the quality of data obtained using different measurements of the same characteristic. Rather than assuming, like the Census approach, that respondents have true states corresponding to the categories of a questionnaire item, the Rasch approach assumes that measuring instruments and survey respondents vary continuously on one or more common dimensions called latent traits. Unlike the Census approach, the Rasch approach requires that the properties of measuring instruments be invariant across different subclasses of respondents, generating parameter estimates that are sufficient statistics for elementary discrete sampling models. The different conclusions that can be drawn from the Census and Rasch approaches are illustrated by an evaluation of questionnaire items designed to measure the limitation or prevention of work because of physical or mental disability."
Americas↗
An overview of demographic analysis as a method for evaluating census coverage in the United States.
"Since the 1950 U.S. census, demographic methods based on the fundamental balancing equation of demography have played an important role in the evaluation of the census net undercount. Application of this set of methods, called demographic analysis, results in national estimates of the net undercount for age-race-sex groups. Although results of demographic analysis are readily available in Bureau of the Census publications, the procedures used to estimate each of the components of population change are less well-known. In this paper we review the historical foundation of demographic analysis, beginning with Coale's 1950 census evaluation project and concluding with the recent evaluation of the 1990 census. We examine each of the components of the method, how their estimation has changed over time, and how they were estimated for the 1990 census."
Americas↗
Estimating adult mortality from a census based method.
"In this paper a simple method is presented to derive current adult mortality level. The sensitivity of estimates to various forms of data error is considered, and procedures are proposed for removing errors resulting from differential census coverage completeness and from age misstatement. The estimated life expectancy at age 5 derived from the method seems plausible." The method is applied to census data for Bangladesh to estimate adult mortality for the period 1974-1981. (summary in FRE, ITA)
Adult↗
Bias measuring mortality gradients by occupational class in New Zealand.
BACKGROUND: Socioeconomic differences in mortality in New Zealand have traditionally been measured using occupational class from mortality data (based on usual or last occupation) as the numerator, and class from census data (current occupation on census night) as the denominator. Such analyses are prone to numerator-denominator bias. Record linkage of census and mortality data in the New Zealand Census-Mortality Study (NZCMS) allows analyses of 'linked' data that will avoid numerator-denominator bias, but may be prone to other biases. OBJECTIVES: To determine differences in the assignment of occupational class between census and mortality data; to investigate biases in the observed association of class with mortality using linked census-mortality data; and to compare the class-mortality association using unlinked versus linked census-mortality data. METHODS: Census records for males aged 25-64 years on census night 1991 were anonymously and probabilistically linked to 5,844 out of 8,145 eligible deaths occurring in the second and third years following census night. RESULTS: (by objective) Only 47% of linked deaths had an occupation recorded on census data, compared to 84% on mortality data - a census to mortality ratio of 0.56. Relatively fewer deaths were identified as class 4 on census data (census to mortality ratio of 0.45) compared to other classes (ratios 0.55 to 0.64). Linkage bias: A lower likelihood of 25-44 year old deaths (but not 45-64 year olds) from lower socioeconomic classes being successfully linked to a census record meant that analyses using linked census-mortality data underestimated the class-mortality association. Bias due to exclusion of economically inactive: Analyses on linked-census data (using current occupational class) considerably underestimated the estimated association of usual occupational class with mortality. The strength of the association of class with mortality according to linked census-mortality data (and adjusted for the above two biases) and unlinked data were roughly comparable. CONCLUSION: Differences in the recording of occupational class on census and mortality data in New Zealand mean measuring mortality differences by class is thwart with difficulty. If one assumes that biases for any particular method of analysis are similar over time, or one carefully adjusts where possible for bias, using occupational class to monitor trends in socioeconomic mortality gradients may be valid.
Adult↗
Appraisal and adjustment methods for demographic census data.
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Censuses↗
Advantages and challenges of using census and multiplier methods to estimate the number of female sex workers in a Chinese city.
Using census and multiplier methods to estimate the size of the population of female sex workers (FSWs) in a small city in western China, this study compared the advantages and challenges of the two methods. It was estimated that there were about 1,500 FSWs within the urban area using the census method, which was significantly lower than that estimated by the multiplier method (2,500). Each method has advantages and limitations, and could be applied to different situations. The census method is less time and resource consuming in smaller regions and has a tendency to underestimate, and therefore, the result can be viewed as a low limit. It is useful in a local setting, for example, when estimations are needed for planning HIV/AIDS prevention programmes in a single city. Using existing information or resources, multiplier method could be used to produce estimates for a large geographic area or at a national level.
Censuses↗