BAL is the governance token of Balancer. Every week, 145,000 BAL are distributed, where 45,000 BAL is distributed to the prioritized BAL stakers, and 100,000 BAL is then distributed to all liquidity providers per weighted sum of liquidity. (Each liquidity pool has a weight assigned by Balancer depending on the kinds of tokens in the pool, the ratios, and fee amount.) There are five factors in the BAL distribution mechanism: Fee factor, Ratio factor, Wrap factor, Cap factor, and BAL staking boost. For detail please refer to this article by Andy.