IR35 - audit targets and numbers

Have seen info on how many and why somewhere very recently but buggered if I can remember where. Have a search on accountingweb and shout99.

Know from personal experience that the CT mob do look at details of expenditure in the accounts (may be an argument for using the abreviated form) and may make enquiries themselves or notify the personal tax gangsters. There is not a hard and fast separation.

I know there have been many IR35 positings on what it is, how to avoid it, etc., but I have never seen anything on two topics :
1) how many people are actually audited each year?
2) how does the IR choose its audit targets?
2a) based on the industry your Ltd is in?
2b) based on number of employees (does it know this?)?
2c) based on comapny turnover?
2d) based on something else?

In reading all the articles and postings, you can't help getting the impression that the IR is auditing just about every Ltd company in the UK (which is clearly not the case). Surely only a very small percentage (1-3%?) of all one-man Ltds are even questioned by the IR.

And how do they put the whole picture together if they receive (separately) a coroporation tax return and a personal income tax return? Yes, on the personal income tax return you have to indicate your employer, but I don't think you need to state that you own more than 5% of the shares.