Although only residents of Scotland can decide the outcome of the referendum, a "Yes" vote will mean changes for the whole of the UK - and one of the greatest will be to do with the physical size of the country itself.
So an already busy country would suddenly become much more crowded, statistically at least.
Economy
Scotland contributes some Â£106.3bn of goods and services in "Gross Value Added" (GVA) - the key measure by which the Office for National Statistics records regional economic output in the UK.
The UK's total GVA, which was some Â£1,383bn in 2012, according to ONS figures.
The effect of Scotland - and its population - leaving the UK would be a small increase in GDP per head of some Â£117.
The value of Scotland's exports to the rest of the world, excluding that to other UK nations, accounted for some 7% of the UK total in 2012.
Scotland's 59 seats in Westminster would disappear if the country votes "Yes" in September, and this could have a drastic impact on future governments.
Modelling the result of the 2010 general election minus Scotland's 59 Westminster seats would have seen David Cameron secure a modest but workable majority of 21. Labour would lose their 41 seats north of the border, while the Lib Dems would drop by 11.
In this alternate 2010 universe, the House of Commons would have looked like something like this.
Life expectancy
Scotland has long suffered lower life-expectancy rates than other parts of the UK, with social problems and pockets of severe poverty cited as factors.
Current UK figures show that men can expect to reach 78.7 years and women 82.6 years.
But if Scotland left the effect would only be a small statistical shift, with men gaining a potential extra 0.4 years (4.8 months) and women 0.3 years (3.6 months).
By comparison with the EU; life expectancy for men is highest in Sweden, where men can expect to reach 79.9 years, while women live longest in Spain (85.1 years).
Despite this, recent statistics for Scotland appear to show an improvement. [Click here]
An earlier version of this article misrepresented some data on life expectancy, GDP and exports. This has been amended.
If Scotland votes for independence on 18 September, what would it actually mean for the rest of the UK?