The First Minister said the single most important statistic is the lack of population growth compared to England.
Speaking in Arbroath, he said protecting the NHS, ending austerity and increasing the population were the opportunities a Yes vote offered to Scotland.
He said: "The first opport-unity is the chance to protect our NHS. In Scotland, because we control health policy, we have been able to resist the Westminster privatisation drive. But we don't control Scotland's budget.
"So when the Tory-led Westminster government privatises services and cuts state provision - those cuts are passed directly on to Scotland."
He said Scotland had the opportunity to take power from the Westminster political elite, adding: "The second opportunity is to end Westmin-ster's assault through auster-ity on our poorest and most vulnerable citizens. A government Scotland didn't vote for launching an assault on the poor: you could call it the worst of both worlds."
Mr Salmond, however, said the large number of people leaving Scotland to further careers was the main concern.
He said: "If I had to pick a single statistic which shows why Scotland needs independence, it is this one: Scotland's population has increased by just over 10% in 100 years from 1901 to 2001.
"Over the same period the population of England increased by almost 60%."
He said that many will still want to leave and said that opportunity would still exist.
But he added: "But there's something wrong when almost 70,000 people leave Scotland every year - more than half of them aged 16-34."