Standard statistical criteria are required in order to maintain the accuracy and objectivity of statistics, and to improve their mutual comparability and usage. As one form of such criteria, the Japan Standard Occupational Classification has been established by classifying occupations according to the similarities between jobs undertaken by individuals and arranging them systematically, in order to express the results of statistical surveys for each individual occupation.

   The origins of the Japan Standard Occupational Classification can be traced to the Occupational Classification used in the 1st National Census, which was conducted in 1920.

   This Occupational Classification was closer to an industrial classification in today's terms, with the addition of some occupational details. At the time, there was no clear distinction between the concepts of occupational and industrial classifications, the latter merely being conducted under the name of the former. The distinction between occupational and industrial classifications was first made in the 3rd National Census in 1930. Then, from the 5th National Census in 1940 onwards, the occupational classification used in the Census was prepared separately from the industrial classification. In the 2nd National Census in 1925 and the 4th National Census in 1935, meanwhile, there were no data specific to different occupations.

   The impetus for the Occupational Classification to be established in its present form was provided by the World Census proposed by the United Nations in 1950. Japan took part in the Census, and, at the suggestion of the occupying forces (GHQ), a Central Planning Commission was set up within the Cabinet's Statistics Commission in 1950. Research on the various classifications was now promoted as a basic operation in the Census execution plan. For this, along with the various special working groups, an Occupational Classification Special Working Group consisting of a committee, a steering group and a sub-committee was set up.

   This Working Group was responsible for preparing the Occupational Classification for the National Census in September 1950, and then continued to prepare standard classifications. For this, a Technical Committee on Standard Occupational Classification was newly appointed to pursue research.

   Following a reform of administrative organs, the Statistics Commission's Occupational Classification Expert Working Group became the Occupational Classification Expert Working Group of the Statistical Standards Department in the Administrative Management Agency from August 1952, though its organizational setup remained the same. In March 1953, a draft proposal for the Japan Standard Occupational Classification was published. This proposal was later re-published in March 1957.

Meanwhile, as part of the aforementioned reform of administrative organs, the Statistics Council was set up as a consultative body to the Director-General of the Administrative Management Agency in August 1952. At the 1st Meeting of the Statistics Council in September of that year, an inquiry was made on establishing standards for occupational classification used in statistical surveys (Inquiry No.2: On the Establishment of Standards for Occupational Classification Used in Statistical Surveys), as well as on the establishment of standards for industrial classification, product classification, regional classification and buildings classification.

   In response to this, an Occupational Classification Expert Working Group was set up within the Statistics Council in November of the same year, and started to deliberate on the establishment of the Japan Standard Occupational Classification.

   After this, the Occupational Classification for the National Census was created by the Statistics Bureau of the Prime Minister's Office in 1955. In 1958, the International Labour Organization (ILO) established its International Standard Classification of Occupations (ISCO), and deliberations on the Japan Standard Occupational Classification also took such experience and research into account.

   Based on this background, a report on the establishment of the Japan Standard Occupational Classification was made by the 90th Meeting of the Statistics Council in March 1960, and in response to this, the Administrative Management Agency established the Japan Standard Occupational Classification in the same month.

   Once the Japan Standard Occupational Classification had been established, considerable changes came to be observed in occupations as a result of shifts in socio-economic trends, causing a divergence from reality when applying the standard classification. Moreover, in 1968 the International Labour Organization (ILO) revised its International Standard Classification of Occupations (ISCO) (a draft revision was adopted at the 11th International Conference of Labour Statisticians (ICLS) in October 1966, and approved at the 168th General Assembly in February-March 1967). Therefore, a revision was planned, and an inquiry on revising the Japan Standard Occupational Classification was made at the 188th meeting of the Statistics Council in May 1968.

   A report to this inquiry was made at the 209th meeting of the Statistics Council in February 1970, and in response to this, the Administrative Management Agency carried out the 1st revision of the Japan Standard Occupational Classification in March of the same year.

   Following this, the 2nd revision was made in December 1979, the 3rd revision in 1986, and finally the 4th revision in December 1997, to keep step with changes in occupational structure accompanying shifts in socio-economic trends.

   The main aim of the 4th revision was, while basically respecting the existing system of classification as far as possible, to ensure that the classes are more widely used as standard criteria when drawing up and using various statistics related to occupations. To this end, the system of classification, class titles, descriptions and illustrations of content have been changed. Of these changes, the main examples of new, abolished, divided, merged and transferred classes are as follows.

(New)			(Old)
03	Mechanical / electrical engineers		03	Mining & manufacturing industry technicians
04	Mining & manufacturing industry technicians (except mechanical / electrical engineers)
034	Electrical engineers		035	Electrical engineers
035	Telecommunication engineers
09	Public health nurses, midwives, nurses		06	Health care workers (except doctors, dental surgeons, veterinary surgeons, pharmacists)
10	Medical technicians
11	Other health care workers
101	Diagnostic radiographers		064	Diagnostic radiographers,Clinical laboratory / medical technologists
102	Clinical laboratory technologists,medical technologists
104	Dental hygienists		066	Dental hygienists/ Dental technicians
105	Dental technicians
301	Passenger / freight clerical workers		301	Transport clerical workers
302	Transportation management clerical workers
392	Left luggage handlers		452	Left luggage handlers,commodity hire workers
393	Commodity hire workers
76	Construction skeleton workers		92	Construction workers
77	Construction workers (except construction skeleton workers)

(New)			(Old)
361	Cooks		353	Bar, cafe and restaurant owners (who prepare food and drinks themselves)
			421	Chefs
			422	Cooks (except chefs)
431	Crop farming and sericulture workers		551	Crop farming workers
			552	Sericulture workers
451	Fishery workers		571	Ocean fishery workers
			572	Freshwater fishery workers
461	Electric and diesel engine drivers		601	Electric engine drivers
			602	Diesel and steam engine drivers
462	Electric and diesel car drivers		603	Diesel car drivers
			604	Electric car drivers
501	Radio communication technicians		641	Radio communication workers
			642	Radio technicians
I-1	Manufacturing and production workers		I-2	Ceramics, earth and stone products, metal materials and chemical product makers
			I-3	Metal product and machinery makers
			I-4	Other product makers
629	Other food makers		779	Other food ingredient makers
			789	Other food makers
64	Spinners and weavers		80	Silk reelers
			81	Spinners and weavers
641	Roving and spinning workers		802	Blenders
			803	Rovers, spinners
648	Rope and net makers(fiber)		817	Rope, cord and string makers (fiber)
			818	Net makers (fiber)
649	Other spinners and weavers		809	Other silk reelers
			819	Other spinners and weavers
672	Papermakers		842	Mechanical papermakers
			843	Manual papermakers
693	Plastic product shapers and processors		864	Plastic product shapers
			865	Plastic product processors
I-3	Mine workers, construction workers and laborers		I-1	Mine workers
			I-6	Construction workers
			I-7	Laborers
75	Mine workers		65	Mine and quarry workers
			66	Other mine workers
751	Miners		651	Miners
			652	Coalminers