Utilize the input text as a context reference, choose the right relationship between halved and half 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.

Prior to 2012, oil exports provided half the Iranian government's revenue and made up one-fifth of the country's GDP; its exports have been more than halved since.

Answer: product_or_material_produced