Keiretsu are a network of companies that have developed over the past two decades as a way for large companies to extend their reach and grow their businesses. In order to understand the keiretsu phenomenon, it is important to first understand the history of Japanese business.

The origins of the keiretsu can be traced back to the Meiji period (1868-1912), when Japan started to rapidly modernize and industrialize. At this time, there were a number of large companies that were able to merge and form conglomerates, known as keiretsu. The main reason for this was that the new companies were able to share resources and pool their expertise in order to compete against the larger foreign companies.

The keiretsu phenomenon continued to grow during the Taishō period (1912-1926), as the country experienced a period of stability and growth. This was because the government promoted the keiretsu as a way to help stabilize the economy and ensure that businesses did not become too powerful.

The keiretsu phenomenon began to decline during the Shōwa period (1926-1989), as Japan experienced a period of economic recession. This was because the keiretsu were unable to compete against the larger American and European companies, which had started to enter the Japanese market.

The keiretsu phenomenon regained popularity during the 1990s, as the country experienced a period of economic growth. This was because the keiretsu were able to pool their resources and offer their clients a variety of services that were not available from the larger foreign companies.

The keiretsu phenomenon is still present today, as many large Japanese companies have formed a network of related companies known as a keiretsu. This network can help these companies extend their reach and grow their businesses.

The Japan Big and Diverse Industries Directory is a reference point for unclassifiable large corporations that produce a wide range of unrelated products. At the end of the Pacific War, the zaibatsu (business conglomerates) were broken up but over the years theses large group of companies reemerged and were a guiding force in the rapid economic rise of Japan.