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IPS153 John D.
then makes redundant the requirement to estimate the demographic
components of change to obtain the following years population estimates.
All that remains is to obtain an estimate of gross population flows in a manner
that is coherent with the net population flows to ensure coherence in the
system of population estimates. We label this type of approach a stocks first
based approach in that population estimates are first estimated before
deriving the flows using the stocks as an input.
This paper presents the methodological approach proposed in the
PECADO project to estimate population flows when SPDs are incomplete.

2. Methodology
2.1. PECADO Project Overview
The project proposes a new system of population estimates based on DSE
methodologies. The system first estimates population stocks before
considering estimation of gross population flows. There is no CPR in Ireland
to underpin public administration systems. However, there is a system of
official Person Identification Numbers (PIN) used by persons when engaging
with public administration systems.

2.2. Estimating Stocks - population size
The PECADO project approach to estimating population size can be
summarised as follows:
Compile an Statistical Population Dataset (SPD) based on Signs of Life
(SoL) An SPD is a dataset that, in theory, contains one record with attributes
for each person in the population. In practice, an SPD may have under
coverage and over coverage with respect to the population. In the PECADO
project, the SPD is compiled with respect to each calendar year. The SPD
contains a record for each person where there is significant evidence that the
person is resident in the State in the calendar year. This evidence is typically of
the form of a transaction, e.g., paying tax, receipt of child benefit, enrolled in
education, receiving public healthcare etc.. Administrative data sources are
chosen to cover the different life stages from the cradle to the grave; births,
child benefit (universal payment), education (primary, secondary and tertiary),
employment, self employed, public health care, pensions and deaths. A
Protected Identifier Key (PIK) is used to link and summarise the records such
that there is only one record for each persons where one or more Signs of Life
are identified. The PIK is an encrypted form of the PIN and preserves linkage
capabilities across data sources and over time while minimising privacy risk by
eliminating the need to use identifiable information. Linkage error is
considered minimised as it is based on a high quality PIN. By design, the SoL
approach eliminates over coverage from the SPD, leaving only undercoverage

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