Re: Where's your sense of balance?
I suspect the home office has a fairly good idea of how many people are entering and leaving the country within a margin of 1-2% to account for known problem areas (ie. The Irish border allowing "tourists" to enter the UK via Northern Ireland or errors where border control mistakes are made).
The real problem for the home office is "the lie" - how big is the actual number versus the publicly available number? How do the methods used to calculate these numbers differ from reality?
I'm not suggesting conspiracy, just that bureaucracys short term fudges to please a political master often backfire horribly and the truth becomes the enemy.