Motivation

Inputs:

• Japan Statistics Bureau (SBJ) estimates population, annually, by five-year age bracket, as of 1 October, from 1920. An intercensal adjustment is applied to the all-ages total. (Example: VSQPOPTUA.IJPN)
• SBJ estimates population, monthly, by broad age bracket, from October 1996. (Example: VSQPOPT1564UM.IJPN)
• The World Bank projects population, annually, by broad age bracket, as of mid-year; from 1960 to 2050. (Example: WBKJSPPOP0014TOUA.IJPN)

Points where our estimates could be improved:

• Our quarterly estimates, when converted to annual, did not align with the annual series above.
• Our estimates did not account for the census breaks in the age brackets (SBJ).

Response

New method:

1. For annual age brackets (SBJ), adjust for census breaks.
2. For monthly age brackets (SBJ), adjust for census breaks.
3. Seasonally adjust (2).
4. Frequency-convert (1) to daily, by setting the 1 October period of the output to the value of the input, with cubic interpolation over the remaining daily periods. 
5. Frequency-convert (3) to daily, by setting the first day of each month of the output to the value of the input, with cubic interpolation over the remaining daily periods. 
6. Forward-extend the daily estimate (4) using the growth rates from (5). 
7. Frequency-convert from daily to quarterly year-end. 
8. Frequency-convert the World Bank projections from annual to quarterly, by setting the Q2 value of the output to the value of the input, with cubic interpolation over the remaining quarterly periods. 
9. Forward- and backward-extend (7) using the growth rates from (8). 

What you will see:

• All periods revised.
• All-ages population lost one quarter of history (1920Q3 to 1920Q4).
• The three age brackets gained five quarters of history (1961Q3 to 1960Q2).

Properties

• Measurement: Thousands of persons (Ths. #)
• Adjustment: Seasonally adjusted (SA)
• Geo coverage: Country
• Native frequency: Quarterly
• Start date: 
• All ages: 1920Q4
• Age cohorts: 1960Q2
• Horizon: 2050Q3

The estimates reside in the historical catalog (Japan » Demographics » Population » Moody's Analytics Estimated » Population projections) and are: 

• RJPOPQ.IJPN     = Population - Total, (Ths. #, SA)
• RJPOP0014Q.IJPN = Ages 0-14
• RJPOP1564Q.IJPN = Ages 15-64
• RJPOP65GQ.IJPN  = Ages 65 and older

Method: Please see also the background documentation in Mnemonic 411.

See also

• New Data: Japan - Population (M) by age (Mar 2019)
• New Estimates: Japan - Population projections by age (Sep 2017)
• New Data: Cross-country - World Bank population projections (Mar 2017)
• New Data: Japan subnational - Population by age cohort (Oct 2013)