McWilliams has coined several terms which have become part of everyday Irish speech, such as "ghost estates" and "breakfast roll man". In January 2007, McWilliams was selected as one of 250 Young Global Leaders by the World Economic Forum and is a regular in the international speaker circuit.
McWilliams was born in Dún Laoghaire in 1966 and was raised in Windsor Park, Monkstown, Dublin. His father, of Scottish descent, worked in a chemical and paint factory but was unemployed for periods while David was growing up. His Cork-born mother was a teacher. He is married to Sian Smyth, a former corporate lawyer, who is from near Belfast. They live in Dublin.
McWilliams attended Blackrock College in Dublin. He then graduated from Trinity College, Dublin, with a degree in economics (1988). His Masters in economics is from the College of Europe, Belgium (1989).
Between 1990 and 1993 he worked as an economist at the Central Bank of Ireland. McWilliams moved to London to work at UBS as a senior European economist and head of Emerging Markets research for Banque Nationale de Paris. From 1999 to 2002, he was an emerging markets strategist with a New York-based hedge fund, Rockwest Capital.
Since returning to work in Ireland, he presented a current affairs programme called Agenda on TV3.
He hosted the breakfast show on NewsTalk 106, a Dublin radio station, from the station's beginning in 2002 until the station replaced him with Eamon Dunphy in September 2004. Soon after, McWilliams started presenting The Big Bite, a topical afternoon discussion programme on the television station RTÉ One. He writes weekly economics columns in The Sunday Business Post and Irish Independent newspapers and appears regularly on TV and radio on economic matters.
McWilliams has written four best-sellers, The Pope’s Children, The Generation Game, Follow the Money and The Good Room. He has written and presented documentaries in Ireland and Australia, not just on economics topics but also exploring the Republic of Ireland’s relationship with Britain and championing Ireland’s left-wing and first female President Mary Robinson.
In 2010, he staged "Outsiders" a part stand up, part discussion, part social observation at the Abbey Theatre, Dublin.
McWilliams hosts Leviathan: Political Cabaret, a live discussion, political cabaret and satire event which features at the Electric Picnic festival every year from 2005 to 2013.Kilkenomics
He co-founded Europe’s only economics festival Kilkenomics in 2010 which combines economics with standup comedy.
McWilliams has worked with another way of looking at current events in economics using his Punk Economics Series of animated videos published on YouTube and also uses animations, music and video in his online economics course Economics without Boundaries.Dalkey Book Festival
He co-founded the Dalkey Book Festival with his wife, Sian.Global Irish Forum
McWilliams conceived The Global Irish Forum, now in its fourth year. It is an event where businesses and leaders, both at home and abroad can work together and contribute to Ireland's economic recovery, and to examine ways in which Ireland and its global community could develop a more strategic relationship with each other, particularly in the economic sector.
Mc Williams has advocated much closer relations between Ireland and its Global Tribe and believes that Irish citizens abroad should have the vote in Irish elections.
He was the first economist to see that the Irish boom was nothing more than a credit bubble and one of the very few to accurately predict it would all end in a monumental crash with bank failures, negative equity and rising unemployment and emigration.
He has never come out in support of any political party in Ireland.
In 2003, on RTÉ 1 he argued that the housing boom was nothing but a “confidence trick” foisted on the Irish people by “an unholy alliance of bankers, landowners and a pliant political class” which would collapse resulting “in a generation in negative equity”
Having predicted the crash, McWilliams sees debt forgiveness and large debt for equity initiatives as a way of reducing personal debts. These ideas are explored extensively in “The Good Room”.
McWilliams questions Ireland's continued participation in the Economic and Monetary Union of the European Union in his books. In an interview with Irish broadcaster Marian Finucane, on RTÉ (17 January 2009) and reported in the international press, McWilliams argues: "What I am saying is, that in Europe, if Ireland continues hurtling down this road, which is close to default, the whole of Europe will be badly affected, the credibility of the euro will be badly affected. .. It is very essential that we go to Europe and say we have a serious problem. … the way we get out of this is either – there are two options – either, we default, or we pull out of the euro. If we have a single currency, there are obligations and responsibilities on both sides. The idea that France and Germany can just hang us out to dry – as has been the talk the past few days – should not be taken lying down."
McWilliams was initially supportive of the bank guarantee of September 2008, describing Brian Lenihan's acion as a "masterstroke" and claiming that by "coming up with a unique, Irish plan -- guaranteeing all deposits -- instead of importing a failed solution from abroad, he has instilled confidence in the Irish financial system." McWilliams even predicted that it would "obliterate[s] " the hedge funds who were short selling the Irish financial sector.
He maintained that the bank guarantee should have been rescinded as originally envisaged rather than prolonged, saying: Rescind the guarantee. It was due to expire last September and was always supposed to be temporary. This guarantee should not have been open-ended and all-encompassing. It should have copied the Swiss and Swedish model, where those countries lent the credibility of the state to the banks. Unfortunately, our Government didn't so much lend the State's credibility to the banks as give it to them unconditionally.
McWilliams said that, providing the banks were reformed, some sort of “bad bank” would be necessary. One idea is to divide our banks into good and bad banks. We could set up one or two bad banks, which would be "financial skips" into which we throw bad loans. In 2009 McWilliams criticised NAMA as proposed, and was in turn criticised by Brian Lenihan. The Minister for Finance took the unprecedented step of attacking the commentator in a full-page editorial piece in the Irish Independent.McWilliams' style and accent, and reputation from Trinity College student days, have led some commentators to believe he is the archetypal role model for Paul Howard's Ross O'Carroll-Kelly series of books. McWilliams is regularly lampooned in the satire TV show Irish Pictorial Weekly.
Comments are occasionally made on McWillams' capacity for self-publicity, describing him as the David Beckham of Irish media.
McWilliams has been 'twinned' with David Caruso by some elements of the Irish media, mostly in reference to Caruso's CSI: Miami character.
In January 2007, McWilliams was selected as one of 250 Young Global Leaders by the World Economic Forum.