For those who are wondering how bandwidth allocation is calculated:
(max_virtual_bandwidth * (vesting_shares + received_vesting_shares) / total_vesting_shares) / 1000000

While max_virtual_bandwidth is calculated :
number_of_blocks_per_week * maximum_block_size * current_reserve_ratio.

current_reserve_ratio fluctuates in response to new transactions.

Your vesting_shares are more or less steem power and received_vesting_shares is your delegated steem power.

So in conclusion the total bandwidth you get allocated depends on how much of the total steem power you have and the amount of transactions inside the blockchain in the last week.

Hope this was helpful :)