In this case, Wikipedia is just using another organisation's map - that of Transparency International, who have been at this a long time, and are reputable.
The reason it's reported as a Corruption Perception Index is because it measures how much corruption impacts on daily lives - how often you're faced with a request for a bribe, how often you find you have to resort to the use of influence to get something that should be yours anyway, whether you have to schmooze, bribe, or influence to get government contracts, and so on.
Measured in those terms Ireland
is extremely clean - you can spend years in business or employment here without ever using influence or bribes or seeing anyone else do so at the level of daily life. People grumble about the public service being slow, but you can't walk into the Passport Office with a little extra above your fee and jump the queue. If a Garda stops you for driving drunk, a little bit of folding stuff won't sort the matter out, and reference to your influential friends will likely make things worse, not better. People may believe their TD "gets things" for them, but 99 times out of a hundred all the TD does is get them what they could have got themselves with a little more patience and intelligence.
At the top level, yes, there's a golden circle, just as there is in every country, because there's a relatively much smaller number of senior and influential positions, and everybody gets to know each other. You'll find the same thing in any relatively small profession or industry - there's a circle of people at the top of Irish botany, for example, but nobody cares about that. And yes, the political parties look after their supporters, and make sure that legislation is friendly for those industries that are supportive of them - but that's what you might call "transparent corruption". You vote for
FF, you
know that
FF will favour the builders - vote for Labour, you know that Labour will favour the Unions. We also know Ministers will try to steer grants towards their constituencies.
And then there's planning - but even there, it's not something that affects the ordinary member of the public directly. You apply for planning permissions, and by and large you'll get it according to the rules, or not. The corruption comes largely in the original zoning - and zoning corruption, plus corrupt permission for large projects, constitutes almost the whole of Irish corruption. Unfortunately, the results of planning corruption affect the whole of Irish life, because they breed waste, dysfunctional public services, impossible public transport problems, grotesque commuting times, overloaded schools - the list goes on, and the results are of such high visibility as to give the inaccurate impression of
pervasive corruption throughout Irish life.