December 2

Pt - Po = (B-D) + (I-O)

( Change in Population ) = ( Natural Decline, Births - Deaths) + ( Net Immigration)

I-O= ( Pt - Po) - (B - D)

following a cohort of of people aged 30-34 in 2005 to the age of 35- 40 in the year 2010:
How many of the "N" people will be alive five years later?

If all were 30: l35 / l30
If all were 34: l39 / l34

Approximate by assuming all are 32.5: l 37.5 / l 32.5
survival fraction (approx) = l37.5/ l 32.5

= .5( l35 + l40)/ .5 ( l30 + l35)
= 5L35 / 5L30

3 Ways to Estimate Using S= 5L35 / 5L30

1) forward : compare SxN expected 35-40 year olds in 2010 to the actual count

2) backward: take (1/S) x actual count of 35 - 40 year olds in 2010 and compare to N

3) average: 1 + 2

What proportion of 30-35 year olds will be alive 5 years later?

5L30 = 491,460
5L35 = 489,248

S= 489,248 / 491,460 = .99550

observe 22,819 30-34 in 2005
23,016 35-40 in 2010

1) forward: expected 35-39 in 2010 = (.99550)(22819)
= 22716

observed 35-39 in 2010 = 23016

observed - expected = 300 ( net migration )

2) backward: expected 30 - 34 in 2005 = 22819
observed 30-34 in 2005 = (1.00452) (23016) = 23120

observed - expected = 22819 - 23120 = - 301

301 net migrants

3) average : 300 + 301 / 2 = 300.5

What percent of 30-34 year olds will survive the next 30 years to be counted as 60-64 year olds?

sL60 / sL30 = 443296/ 49460 = .90199

page revision: 0, last edited: 06 Dec 2010 19:54