The paradox here is that the Republic's rapprochement with Northern Ireland was made easier by the stagnant and declining economic fortunes of the Republic. One of the stumbling blocks for negotiations between the Republic and Northern Ireland in the post-Treaty decades was there was a fear that the more populous Catholic Republic would swallow up the North if negotiations started. Thus NI Prime Minister O'Neill felt less of a threat engaging with his Republican counterpart Lemass if it was clear that the Republic was not a dynamic polity. The latter Taoiseach also benefited from the Republic's decline because he could package the new contacts with NI as part of a wider break from failed policies. The population figures are relevant because they show the consequences of De Valera's policies cutting Ireland off from the rest of the world. De Valera promoted a vision of a pastoral Ireland with a "contest of athletic youths and the laughter of happy maidens" that was a throw-back to nineteenth-century Romantic images and politics. This approach did not exactly create a prosperous Republic and created an image of the Republic that it was a cultural and economic backwater. This period of the Republic's economic doldrums stoked a new era of Irish migration that lasted roughly until the "Celtic Tiger" of the 1990s. So Lemass managed to parlay a weak position (ie stagnant economy and other factors) as a justification to make a diplomatic breakthrough.

But breakthroughs are common in Irish political history, but sustaining them is not. Lemass did lay a lot of groundwork for later economic upturns and a more outwards-looking foreign policy, but these came to pass well after he had left the political scene.