Page 301 - Invited Paper Session (IPS) - Volume 1

IPS153 John D.
population flows are made up of Inflows (Births plus Immigration) and
Outflows (Deaths plus Emigration). The PECADO system to estimate gross
population flows can be summarised as follows:
Estimate Stayers in SPD between two consecutive years 1 and 2 The same
DSE methodology is used to estimate Stayers in the SPD between two years
where lists A and B are formed from the PAR and DLD. Stayers corresponds to
the group of persons present in the population in both years 1 and 2.
Gross estimate to obtain estimate of Stayers in population The next step is
to simply gross the estimate of Stayers in the SPD to obtain an estimate of
Stayers in the population. The factor used for grossing is obtained by dividing
the population estimate by the size of the PAR for either year 1 or 2. We make
the assumption that the proportion of Stayers in the population not included
in the PAR is equal to the proportion of Stayers in the population included in
the PAR for the respective year. This is the only additional assumption made.
In making this assumption, we note the impact of any violation of this
assumption will reduce as the coverage of the PAR with respect to the
population goes to 100%. Noting that we can estimate Stayers using the
population in either year 1 or year 2, we can also consider combining the two
estimates to improve precision (reduce variance).
Estimate flows by subtracting Stayers from population estimates The gross
flows can now be obtained using the Demographic Accounting Framework as
follows:
Outflows, year 1, can be estimated by subtracting the estimate of Stayers
from the population size estimate in year 1, Inflows, year 2, can be estimated
by subtracting the estimate of Stayers from the population size estimate in
year 2.
To estimate gross population flows, we consider the population in year 1,
U1, the population in year 2, U2, the population common to both years, US =
U1 ∩U2, the population of Outflows (those in year 1 but not in year 2), UO = U1
\US and the population of Inflows (those in year 2 but not in year 1), as UI = U2
\US. We denote the respective population sizes as N1, N2, NS, NO = N1 — NS
and NI = N2 — NS. DSE methods, as previously described, are used to estimate
N1 and N2 as 1 = / and 2 = / where is the size of list A in
̂
̂
2
1
1 1
2 2

year ( = 1 or 2), is the size of list B and is the size of the match (

∩ ) between list A and list B for year . If we can estimate NS we can obtain

estimates of NO and NI, the gross population flows.=
To estimate NS, we first estimate Ki, the number of Stayers in using

DSE methods and multiply by / , we can use i=1 or 2. We get
̂

̂
= : : for , = 1,2 ≠

:

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