Utilize the input text as a context reference, choose the right relationship between prime and retail from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Experts attributed the return of retail investors and the subsequent performance of mid-cap stocks as the prime reason for the increase in DII shareholding.

Answer: industry