BBC News By Philip Sim image copyrightGetty Images Politicians insist that the Scottish Parliament election on 6 May could be one of the most important in the county's history. But on average, almost half of the electorate don't actually vote in these polls. Who are the Scots who don't take part in the democratic process, and what's holding them back? "The Holyrood voting system means Scottish Parliament election results are always on a knife-edge. That's hard-wired into the system. "So every vote really does matter - and the outcome has never been more important." That was Nicola Sturgeon's summary of the Holyrood election campaign as she launched the SNP manifesto. A crucial contest which could shape the very future of a nation.