The problem with a rankings system is whilst they work extremely well if teams are evenly matched but if a team build up a cushion it takes forever to topple them. Australia did it with Cricket. Between 2009-2011 England lost zero tests series (unless you include WIdies debarcle 2008/9) however despite this they were only made 1st in rankings at the end of that period and because they didn't build a cushion lost it pretty quickly
That is exactly the opposite of the way the ranking system works.
Firstly, you cannot "build a cushion" because there is a limit to how far ahead of other teams you can get (about 7 ranking points at home, 12 ranking pints away) before beating them by less that a 15 point margin) doesn't gain you any points, and the losing team doesn't lose any. The limits are slightly higher for winning margins over 15 points. As things currently stand, New Zealand can only gain ranking points in home matches from South Africa and England (by less than a 15 point margin) and Ireland and Wales (by more than a 15 point margin). The remaining teams carry no ranking point values for New Zealand
Secondly, the top team, even if they are a long way ahead, will fall a lot faster if they lose a match to a much lower ranked team, and that will also depend on other results around them, for example, here are the current rankings as of this post
[TABLE="class: fullRankings"]
<tbody>[TR]
[TD="class: firstColumn"]1[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]93.70[/TD]
[TD="class: detailsCol"][/TD]
[TD="class: addToFavourite"][/TD]
[/TR]
[TR]
[TD="class: firstColumn"]2[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]88.23[/TD]
[TD="class: detailsCol"][/TD]
[TD="class: addToFavourite"][/TD]
[/TR]
[TR]
[TD="class: firstColumn"]3[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]85.83[/TD]
[TD="class: detailsCol"][/TD]
[TD="class: addToFavourite"][/TD]
[/TR]
[TR]
[TD="class: firstColumn"]4[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]85.66[/TD]
[TD="class: detailsCol"][/TD]
[TD="class: addToFavourite"][/TD]
[/TR]
[TR]
[TD="class: firstColumn"]5[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]82.95[/TD]
[TD="class: detailsCol"][/TD]
[TD="class: addToFavourite"][/TD]
[/TR]
[TR]
[TD="class: firstColumn"]6[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]81.71[/TD]
[TD="class: detailsCol"][/TD]
[TD="class: addToFavourite"][/TD]
[/TR]
[TR]
[TD="class: firstColumn"]7[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]80.09[/TD]
[TD="class: detailsCol"][/TD]
[TD="class: addToFavourite"][/TD]
[/TR]
[TR]
[TD="class: firstColumn"]8[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]78.23[/TD]
[TD="class: detailsCol"][/TD]
[TD="class: addToFavourite"][/TD]
[/TR]
[TR]
[TD="class: firstColumn"]9[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]77.11[/TD]
[TD="class: detailsCol"][/TD]
[TD="class: addToFavourite"][/TD]
[/TR]
[TR]
[TD="class: firstColumn"]10[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]75.39[/TD]
[/TR]
</tbody>[/TABLE]
The first three matches of the coming SH season are
Samoa v New Zealand
New Zealand v Argentina
Australia v South Africa
Of New Zealand were to lose
either of these two matches by 15 or more points (winning the other one gains them nothing) they would drop to 90.70. And then if South Africa were to beat Australia by 15 or more points, they go to 89.39. NZ remain top, but they have dropped from 5.47 points ahead of South Africa to only 1.31 points ahead.
The next weekend, its South Africa v New Zealand at Ellis Park. If South Africa win they will go top (90.22) and NZ will drop to second (89.87)
This illustrates that your assertion of a "cushion" for the top team making it difficult to topple them is just plain wrong. The All Blacks have won 38 out of the 42 matches they have played since the last world cup, losing only twice, yet it would only take two losses in a row to knock them off the top.
---------
Some of the posters here are saying that a competition being
"harder to win" is the same thing as being
"tougher". It isn't.
The World Cup is harder to win, mostly because of its knock out nature, but the Ruigby Championship is a much tougher competititon because of the travel and time difference between matches and the higher percentage of matches against top teams. There are no minnows like Portugal, Namibia, Japan, USA or Canada. In the Rugby Championship,
every game is a tough game to win.