The “Celtic Tiger” was an economic movement that happened in the last part of the Twentieth Century. In the early part of the Twenty-first it slowed, then accelerated again for several years before slowing again.
It had many positive effects for the Irish. These included additional jobs, increased incomes, more white-collar jobs rather than those depending on hard labor, more buying of luxuries and essentials, more businesses, and more housing.
Changes, especially rapid ones, always have their downside as well. For example, increased incomes went to the educated and the young and energetic but not to others. The construction boom caused by the influx of people from the country side and from other countries drove up the cost of housing. This was a hardship for those on a fixed income and on those whose wages had not increased to match the housing prices. Immigrants drawn by the Tiger, especially non-whites, met with resentment and sometimes violence.
Mary’s “Irish Renaissance” had its own upsides and downsides – and what was an upside for some was a downside for others. Ireland came to dominate the British Empire, for instance, with obvious winners and losers.