A further question, out of philosophical curiosity; Would you choose differently, if "the person opearating the other lever" would not be a person making moral choices, but a mechanical machine instead? That machine would be making a random choice each time a trolley approaches, 50% of time sending the trolley to the empty track, 50% of time sending the trolley to the track where 7 billion people are tied.

So, if that was the case, you'd have these options:
1. Do nothing, in which case the trolley will kill the 44 million people on the main track.
2. Pull the lever, diverting the trolley onto the side track, in which case there is 50% chance that no-one dies, and a 50% chance that 7 billion people die.

In that case, would you be the only person bearing full moral responsibility of the consequences of either pulling or not pulling the lever? Or would you like to go further up / down the chain of responsibility, asking "well, then, who built that machine operating the other lever? Who gave orders to install that machine there? Who obeyed the orders to install the machine? Who made the decision to tie 7 million people on that track? Who obeyed the orders to tie people on tracks?"