What other duel below international level has commanded an average attendance in excess of 50,000 over the last seven seasons? Fifty thousand? And the rest.
Leinster-Munster over that period have gone beyond that, pushing the average to 52,303, a figure of such monumental proportion that nobody can hold a candle to the pulling power of the ancient Irish tribes, not even the All Blacks.
The figures speak for themselves. In six home Tests since retaining the World Cup, New Zealand's untouchables have averaged 31,744. In six Guinness PRO12 matches and one European Cup semi-final at Croke Park,
Leinster v Munster has topped the All Blacks' total by more than 20,000 per game.
They will top it again at the Aviva Stadium on Saturday afternoon, the only question being by how many. If the gate reaches 40,000, and by the start of the week sales were heading in that direction, the crowd will outnumber eight of the ten Premier League football matches last weekend.
Since transforming their home match from the RDS into an annual event at the Test venue across the road, they have topped 50,000 twice and never fallen below 43,000. Wherever they put it on in Dublin, no stadium is too big, no setting too grand, a point never made more strikingly than when 82,208 jammed into the GAA's steepling cathedral on May 5, 2009.
Leinster won that European Cup semi-final, just as they have won all but one of eight subsequent confrontations with their neighbours in the Irish capital. Of those centre-stage at Croke Park seven years ago, Leinster have four survivors (Isa Nacewa, Cian Healy, Jamies Heaslip, Johnny Sexton) and Munster one (Keith Earls).
When Leinster outpointed their rivals 16-13 this time last year, Sexton accounted for every single one. In doing so he was extending the tradition of a fixture won more often than not in recent times by goalkicking No. 10s, be they blue (Ian Madigan, Felipe Contepomi) or red (Ian Keatley, Ronan O'Gara).
Saturday's meeting will be the 92nd over the last 70 years with Leinster ahead but not by much, 45-41. That it comes with both in the Guinness PRO12 top three on the strength of four wins from five gives the occasion a bit of added spice, not that any will be necessary.
For a South African in Limerick and an Englishman in Dublin it will be a novel experience. Rassie Erasmus prepares for the Big One as Munster's director of rugby, Stuart Lancaster, none the worse but a little wiser for his country's World Cup experience this time last year, as Leinster's senior coach.
While Erasmus presided over a runaway win over Zebre at Thomond Park, Lancaster saw Leinster refuse to buckle in the face of a late Blues' onslaught before ending their winning run in Cardiff last Saturday night
Round 6 brings the first of several Big Weekends throughout the PRO12 calendar, the schedule featuring Irish and Welsh derbies. The other all-Ireland affair takes Ulster to Connacht - the unbeaten leaders against the champions.
They cut it mighty fine against Ospreys in Belfast last Saturday night, Paddy Jackson's late penalty squeezing them home and leaving their Welsh opponents feeling short-changed after scoring the only try of the match.
Blues supporters felt equally short-changed having witnessed their team come up inches short against Leinster after losing a 10-point lead, as well as Sam Warburton with a cheekbone injury. Between them, the two leading Welsh regions lost by the infuriating margin of three points in one match, two in the other.
Now they are preparing to plough headlong into each other. Ospreys expect their highest attendance of the season in Swansea on Friday night when the Blues make the 40-mile journey west along the M4.
The Dragons make a slightly longer trip along the same motorway for their first derby of the campaign at Llanelli. After starting with three defeats, Scarlets will be aiming for a third straight win against opponents undone last week by a relatively new phenomenon, the side-stepping prop.
Alex Allan's nifty footwork and a 20-metre dash under the posts may not have done much for the old-fashioned caricature of a prop as being incapable of singing and dancing at the same time but it proved decisive in putting the Warriors back on a winning road.
The Scottish loosehead found himself in excellent company as one of no fewer than five try-scoring props last weekend. Sam Hobbs got one for the Dragons, Nicky Smith the only one for Ospreys, Werner Kruger for Scarlets in Treviso, Stephen Archer for Munster against Zebre.
Quite what Owen Franks would make of all that is anyone's guess. The All Black tighthead broke a world record last month by avoiding any danger of being shoved over the try line with the ball in his hands.
After 83 Tests without a score to his name, Franks duly ensured that he didn't slip up in the 84th, against the Springboks in Hamilton thereby taking the record from the no doubt suitably relieved Italian prop Salvatore Perugini.
In a PRO12 context, no prop has scored tries of late quite like Dave Kilcoyne - 14 from 69 starts for Munster with one already this season. And nobody ought to be one bit surprised should he embroider Saturday's grand occasion with another…
Guinness PRO12 Final 2017 Ticket Information: Fans can save up to 20% on selected tickets, and prices start at just €30 adults and €5 child, and be booked via www.ticketmaster.ie. For further information visit http://www.pro12rugby.com/final
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