Didn't downvote, but I have the same opinion as those people.
I think it's likely. In fact, by default policies should scale linearly from 10 millions upwards.
Policy that works great in NYC isn't guaranteed to work great in LA. Laws that work well in Dallas or San Antonio might have negative effects in Detroit, Chicago, or St. Louis.
That's why you see huge differences for example between states even in things we expect to all agree on. There's very few national policies that simply scale to all states exactly the same, the military probably being a big one. But things like education, police or fire departments, housing, healthcare or even marriage, can be radically different. But here in the Netherlands? On tons of topics like education, police, healthcare or marriage, it's exactly the same in every single province, because we're pretty much one big state, despite quite large differences between provinces. e.g. 2 hours north-east, I can't understand the local language, here it's mostly protestant but two hours south is mostly catholic. But despite big differences in culture, language, religion, but also industries and demographics, it's extremely homogeneous in policies. To me that says that you can't just scale a policy to 300m like you can to 17m.
Sincerely Swede
Also closing gaps in income inequality, and continued spending by that larger percentage of middle-class population.
Or so history teaches us, which we're rather happy to ignore now.
http://en.wikipedia.org/wiki/List_of_countries_by_tax_revenu...
Wealthy people are the ones who relocate and they don't benefit much from social welfare programs (if you ignore tangential benefits like not getting your car broken into by someone who needs money to eat).