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.

Volumes on the latter more than tripled to 225 million tonnes in the first half of 2015, while swaps volumes almost halved to 88 million tonnes.

Answer: product_or_material_produced