Estimation method
For detail of Lifespan definition, click here.
For detail of Lifespan distribution type, click here.
The methodologies that were used for estimating lifespan distribution in literature can be classified into four types. The features of each methodology are as shown in the table below. For more details, see the literature listed in Research Results section of the top page.
Table. Four methodologies for estimating lifespan distribution of commodities
| Methodology | How to obtain required data | Definition of estimated lifespan | Characteristics |
|---|---|---|---|
|
(1) Estimation from the number of discarded commodities for each life span |
・Survey of discarded commodities at recycling and waste treatment facilities. |
(Domestic) total lifespan |
・Easier to obtain distribution in a certain area, where the surveyed facilities are located. ・Survey must be conducted at many facilities around the country in order to obtain representative estimation. ・Obtained distribution would be biased due to the exclusion of commodities exported or illegally dumped. |
・Questionnaire survey to owners on the commodities that they discarded in the past. ・Utilization of statistical data. |
(Domestic) service lifespan, Possession span, Duration in use | ・Easier to obtain distribution for an entire country. ・The destination of discarded commodities is required in order to clarify the lifespan definition of estimated distribution. ・Obtained data from a questionnaire survey might fluctuate because the survey must rely on owners’ memory. |
|
(2) Estimation from remaining rate derived from the number of commodities in use for each product age |
・Questionnaire survey to owners on commodities in use. ・Utilization of statistical data. |
(Domestic) service lifespan | ・Easier to obtain distribution for an entire country. ・More accurate data can be obtained from the survey of commodities in use. |
(3) Estimation from the number of commodities in use for each product age at the beginning and the end of a certain period |
・Questionnaire survey to owners on commodities in use. ・Utilization of statistical data. |
(Domestic) service lifespan | ・Useful when it is difficult to obtain shipment data for each shipment year (such as for buildings and construction). ・Useful when lifespan distribution does not vary greatly by year. ・Able to estimate distribution for any commodity group and within any spatial boundary. |
(4) Estimation from the total number of commodities in use by using mass-balance principle |
・Questionnaire survey to owners on commodities in use. ・Utilization of statistical data. |
(Domestic) service lifespan | ・Able to estimate distribution from only the total number of commodities in use (not for each age). ・Easier to obtain distribution for an entire country. ・Have to make sure that the definitions of a commodity of concern in different statistics are identical. |