Ireland's next opponents, England, are now the leading northern Hemisphere nation in the rankings after climbing two places to fourth thanks to their 24-22 away victory over France.
The win has seen the two sides swap places with England now occupying the position the other nations crave in order to avoid the prospect of being drawn in the same pool as defending champions New Zealand, Australia or South Africa in the 2005 Rugby World Cup pool allocation draw.
England last occupied fourth spot before last year's Rugby World Cup quarter-final defeat to France and by avenging that loss, they have ensured that les Bleus have slipped three places in the space of two weeks after failing to win on home soil against Ireland or England.
Wales have remained stationary in fifth despite keeping their Grand Slam dreams alive with a 24-3 triumph over Italy at the Millennium Stadium, a consequence of being the home side and ranked seven places and 9.29 rating points above the Azzurri.
The Welsh now face a Grand Slam decider against the wounded French with only one hundredth separating the two sides, and given they lie only three tenths behind England they could have more to celebrate than the coveted clean sweep.
IRB WORLD RANKINGS (as of Monday, March 12):
Last week's positions in brackets -
1(1) NEW ZEALAND 91.43 rating points
2(2) AUSTRALIA 87.99
3(3) SOUTH AFRICA 84.34
4(6) ENGLAND 82.93
5(5) WALES 82.62
6(4) FRANCE 82.61
7(7) IRELAND 80.55
8(8) ARGENTINA 80.28
9(9) TONGA 76.63
10(10) SAMOA 75.81
11(11) SCOTLAND 74.69
12(12) ITALY 73.33