Dr. Enda Shanahan:

There is a large amount of research on this matter in the published literature. The National Bureau of Economic Research in the US, which is a private, non-profit research organisation committed to undertaking and disseminating unbiased economic research among public policy makers, business professionals and the academic community, has repeatedly examined this issue in the US and various other countries.

It has found there is no link between employing older workers and reducing employment for younger workers. It also found that having older workers continue to work does not reduce the wages of younger workers. In the European Parliament, the Directorate-General for Internal Policies of the Union produced something similar in April 2013. The Journal of European Labor Studies, IZA, in Bonn has come up with the same findings. I have umpteen references on this.