Utilize the input text as a context reference, choose the right relationship between impact and CD 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.

The second quarter increase was driven by a decrease in the interest expense due to a combination of lower rates, lower brokered CD balances and a decrease in the impact of the accelerated premium expense associated with calling the remaining brokered certificates of deposits.

Answer: distribution_format