What are the implications of demographic divergence between euro-zone countries?

Euro-zone countries have very different demographic prospects: stable labour force in France, declining labour force in Germany, Spain and Italy; a much larger retired population in Italy than in the other countries. What to expect from this divergence in demographic prospects between the euro-zone countries? It generate s divergence in potential growth rates, which makes it difficult to use a single interest rate; It generate s divergence in countries’ ability to ensure the sustainability of their public debt, as growth gaps are not reflected in yield spreads; It generates divergence between savings rates (a country that ages is expected to have a lower savings rate) and therefore between current account balances; It generates higher public (pension) spending in countries where ageing is more advanced, due to smaller tax bases in these countries (due to the decline in the labour force), leading to significant differences between public finance situations. Altogether, we see that demographic divergence will create strong tensions in the euro zone, by giving rise to divergence between growth rates, debt ratios (bond risk premia), savings rates and current account balances, and public finances.