There's like a middle scale where you're not big enough that Microsoft will go out of their way to whitelist you, but you're big enough that your "send to junk" rate is just high in terms of absolute numbers.
It's certainly not a ratio, it must be based on absolute numbers because I've seen it too many times across too many companies, and the only ones that get away with it are extremely low volume.
Once you have 1,000,000 mails, even a 0.1% mark as spam rate is 1,000 emails. - and some people treat mark as spam as their delete button, certainly more than 0.1% of people. Don't ask me why.
EDIT: on inspection; it's worth noting the mechanism is even more insidious than "people mark you as spam". Microsoft also weighs delete-without-opening as a negative signal. So if you're sending transactional mail (receipts, shipping notifications, invoices) and your users get exactly what they wanted, feel satisfied, and bin it without opening. You've just taken a reputation hit for doing your job correctly. The senders most at risk aren't the ones sending rubbish.
EDIT2; theres a reply to me that I can’t reply to because its [dead]; though the point is valid so I vouched. To them I say: I agree. But you probably want your receipt, and thats the example I gave (for a reason).