Based on what?
If you have in mind the usual source of that claim, that being Dustmann and Frattini's UCL paper, I'd suggest you go take a long, hard look at exactly what the paper says and in particular, the methodology used. It is not based on an accounting type exercise, like a P&L based on complete and accurate data, but on incomplete data, and based on a whole series of assumptions on what costs to include, how to assess, approximate or allocate costs, and for that matter, revenues.
It is an interesting academic exercise but it needs to be seen as exactly that - can academic paper, full of assumptions and artificial treatments. What it is not is an accurate accounting of either revenues or expenditures. If you change those assumptions, the justification for which is very brief where it exists at all, the can come to completely different results.
Moreover, it's worth looking at what the House of Lords said about immigration impact analyses -
That same criticism applies to the UCL paper, and indeed, the paper itself spends a fair bit of time in it's 50-ish pages pointing out the shortcomings, the limited data available, the assumptions made in allocations and so on.
And even if it were 100% accurate and 100% complete, it is still only looking at fiscal impacts and takes no account whatever of either overall impact on the economy or on the social impact. Thus, it ignores other reports suggesting, for example, that immigration impacts on the wages, and employment levels, of the poorest paid.
Let me put that another way. Even if the claim is true, and that overall the fiscal impact is beneficial, it would be prudent to look at the allication of the benefit. For instance, if big businesses, and their owners, benefit hugely from reduced labour costs, but the low-paid suffer from reduced employment levels and suppressed wages then overall there's a net benefit, but at considerable social impact on the poor while the rich get richer.
But hey, immigration must be good because an over-simplified one-line summary says "net benefit", right?
The House of Lords report concluded
Yet, it's astonishing how often a one-line tabloid misinterpretation of Dustmann and Frattini is used to do exactly that.
Be very careful how you use simplified summaries from academic papers to justify real-world decisions because, far too often, those academic papers have assumed and allocated the reality out of the subject in order to make it workable at all. The picture from migration reports is nowhere near as clear as simplistic newspaper reporting would have us believe. Don't believe me either? You don't need to. Go read the actual reports, in full, and pay particular attention to the vast array of caveats they contain.
.....I'm sorry but people are criticising Clegg for not keeping his word over something he had no control over - An election pledge if they won the election - which they didn't and he had to compromise over issues when in a coalition, which is perfectly normal. And then saying Farage is a man of his word when he didn't even resign when he promised he would, something he has full control over. No-one can 'stop' you resigning just by saying we don't accept your resignation.
Goodwill towards Nick Clegg couldn't be higher amongst millennials.