ONE of the biggest challenges facing Scotland is to come under the microscope in Glasgow this week - how our biggest area of public spending might be affected by the constitutional debate.

We spend £21 billion a year on social protection. This goes on the state pension, which takes 45% of the total, and also on a range of other benefits including free prescriptions, free bus travel, unemployment benefits, disability allowances and housing benefits.

To put that into context, in a year in Scotland we spend £19bn on our health and our education combined - around £11bn on health and £8bn on our education. The £21bn represents more than 38% of all the identifiable public spending that takes place in Scotland, some £55bn in total.

This is also the area in which we see the largest non-devolved public spending in Scotland. Through the Department of Work and Pensions the UK Government contributes around £14 million of the £21bn, with the rest paid through the Scottish Government and local authorities.

While there has been some media coverage of issues relating to pensions in an independent Scotland, the overall shape and purpose of the social protection programme has not received as much attention as other issues, such as currency or EU membership, but is a topic which everyone in Scotland should be thinking about.

The Royal Society of Edinburgh has been running a series of events in recent months designed to enlighten the debate around our constitutional future. We do not seek to take sides but to tap into expertise to help inform.

For tomorrow's event at Glasgow's Barony Hall, the discussion is not designed to advocate any policies relating to the welfare agenda. It is intended to provide information and expert commentary about the welfare-related issues which the people of Scotland may wish to consider when deciding if Scotland should be an independent country.

Social protection spending is projected to continue rising as a proportion of all public spending. In Scotland, social protection spending per person is higher than in the rest of the UK. In that sense, Scotland does well from the system, but this is mainly because Scotland has a population ageing slightly faster than the rest of the UK, and has higher levels of payments relating to illness and disabilities.

However, within that brief statement lies a conundrum. The state pension is protected by linking it to specific indices to determine its value is not eroded. With pensioners being protected the pressures are being most keenly felt by those in the working age groups and those with children, particularly in single parent households.

The challenges facing the social protection system will continue to face us regardless of the structure or hue of governments in Westminster or Holyrood, but there are different ways of addressing the challenges and the financial implications.

These will be addressed by experts brought together by the RSE, including leading figures from our universities and anti-poverty groups. We will look at current thinking in the UK at reducing poverty; we will look at welfare policy reforms from other parts of the world; we will examine the fiscal and economic implications of our ageing population; we will look at matters from the perspective of those in receipt of social protection services; and we will look at how welfare policy might be constructed if unencumbered by current polices and commitments.

Attitudes to welfare reform in Scotland and the rest of the UK will also be explored, and these also throw up some interesting tensions. For example, opinion polls generally show people quite like the idea of social spending in Scotland being controlled from Scotland - but the level of entitlement should be the same as throughout the UK.

We will also look at whether there are options for further devolution of welfare powers if Scotland remains part of the UK, as well as the issues which would arise should Scotland become an independent country.