Intuitive answer:

Picture a horizontal line and points scattered around it. If there are many points, the line will be dark and there'll be a cloud around it. If there are few points, you'll get a vague shape and it won't be easy to tell where the line originally was.

Rigorous answer:

print [
len(filter(lambda x: x > 0.6 *per_day,
[
sum([ randint(0,1) for birth in range(0, per_day) ])
for day in range(0, 365)
]))
for per_day in (15, 45)
]

Thoughtful answer: Why would I bother thinking? Fetch me an apple.

Edit: For copulation's sake, whose kneecaps do I have to break to make Markdown leave my indentation the Christian Underworld alone, and who wrote those filthy blatant lies masquerading as comment formatting help?