Posts from March 2026 (35)

Team Ratings for Round 20

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 133 matches played, 102 of which were correctly predicted, a success rate of 76.7%.
Here are the predictions for last week’s games.

Predictions for Round 20

Here are the predictions for Round 20. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Week 7

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 30 matches played, 19 of which were correctly predicted, a success rate of 63.3%.
Here are the predictions for last week’s games.

Predictions for Week 7

Here are the predictions for Week 7. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 12

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 55 matches played, 41 of which were correctly predicted, a success rate of 74.5%.
Here are the predictions for last week’s games.

Predictions for Round 12

Here are the predictions for Round 12. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 4

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 24 matches played, 14 of which were correctly predicted, a success rate of 58.3%.
Here are the predictions for last week’s games.

Predictions for Round 4

Here are the predictions for Round 4. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Week 4

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 21 matches played, 14 of which were correctly predicted, a success rate of 66.7%.
Here are the predictions for last week’s games.

Predictions for Week 4

Here are the predictions for Week 4. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Yesterday I noted RNZ had just quoted an Auckland Transport claim about the cost of driving that was implausible on the face of it, and didn’t seem to have done any checking or provided any explanation.  Today, the same story is in the Herald, with the same  lack of explanation.

Here’s the RNZ quote; the Herald one is almost identical

Auckland Transport said before the Iran conflict began late last month, the cost of public transport was roughly the same as the cost of driving a vehicle with single occupancy in Auckland.

It’s now costing people nearly double to drive their own cars.

“The cost of petrol has risen at least 50 cents per litre since then, with a 15-kilometre single person commute now costing roughly 80 cents per kilometre, which is equal to about $12 for the total trip.”

So where does this come from? In comments to yesterday’s post, David Welch pointed me to the IRD page on the cost of driving.  The “Tier 1” cost in 2024-5 was $1.17/km for petrol cars. That’s higher than 80c/km, and it’s also not the right comparison — it’s an average cost per km. That is, it includes a per-km share of the fixed costs of having a car. Auckland Transport are (or should be) talking about just the extra per-km cost of using the car to commute. Taking a bus won’t make your car loan go away.

The IRD view on the cost of running a car is their “Tier 2” number, which is only 37c/km.   That, interestingly, is close to half the 80c/km that Auckland Transport is claiming. Since they say that this is double what last year’s cost was, their estimate of last year’s cost is interestingly close to the IRD Tier 2 value and might come from the same methods?

I found an estimate of national average petrol prices as $2.66/L  from December last year.  That would be an increase of 44c/L compared to the one Auckland station I checked yesterday.  If, instead, we take Auckland Transport’s “at least 50c/L”, the increase in running costs would be 5c/km for a vehicle that gets 10 km/L, and less than that for a more typical single-commuter vehicle, so again we can’t get the AT figure.

Even without trying to work out and replicate their calculations, however, we can say one simple thing.  Petrol prices have not yet nearly doubled, so they can’t have caused driving costs, however defined, to have nearly doubled.

On the other hand, the conclusion that people should consider switching to public transport is true: we want to save the potentially scarce supply of oil for people and industries who don’t have any alternatives.

Update: Greater Auckland have also reprinted the claim from AT, again without comment.

• RNZ passes on a claim by Auckland Transport  that Cost of driving 15km in Auckland nearly double that of public transport. Specifically, they say we have “a 15-kilometre single person commute now costing roughly 80 cents per kilometre, which is equal to about $12 for the total trip.” That seems a lot?  I won’t claim to be an expert on driving costs, but the nearest petrol station for which I can see data (Mobil on K Rd)  is charging $3.099/litre.  To get 80c/km you would need to use a bit over a 1/4 litre per km (more precisely, 0.258l/km). This is 25.8 L/100km (for our US readers, about 9 mpg).
• The US celebrated Pi Day this week, and there was a niche popular video describing how to estimate π by coin tossing.  Toss a coin until there are more heads than tails. The expected value of the proportion at this point (which is obviously more than 1/2 and at most 1) is π/4, so by repeating this procedure lots and lots of times and averaging the results you can estimate π/4, and thus π.  This is not a good way to compute π, but it’s surprising that it works at all (sadly, the explanation for why it works is not very illuminating)
• From newsroom, “Mazda NZ’s Driving Good promotion promises the company will donate five trees to environmental charity Trees That Count and that “over each vehicle’s five-year warranty term, these five trees will not only mitigate any environmental impact from CO2 emissions, but they will significantly contribute to the ecosystems in which they are planted”.” Whether this is true turns out to be sensitive to your interpretation of “mitigate”.  There is a sense in which planting any trees provides some mitigation of the environmental impact from CO2 emissions, but you might think Mazda was saying something more like “will absorb as much CO2 as the car emits”. If that’s what you think, you agree with Lawyers for Climate Action, who say it would take 41,000 trees to absorb a comparable amount of CO2.
• StatsNZ said “food prices were up 2.5 percent in January 2026 compared with December 2025. The correct increase was 2.1 percent.”  They’ve fixed it, and it didn’t impact the CPI.

Team Ratings for Week 6

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 25 matches played, 15 of which were correctly predicted, a success rate of 60%.
Here are the predictions for last week’s games.

Predictions for Week 6

Here are the predictions for Week 6. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Week 13

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 96 matches played, 62 of which were correctly predicted, a success rate of 64.6%.
Here are the predictions for last week’s games.

Predictions for Week 13

Here are the predictions for Week 13. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.

Team Ratings for Round 3

The basic method is described on my Department home page.
Here are the team ratings prior to this week’s games, along with the ratings at the start of the season.

Performance So Far

So far there have been 16 matches played, 9 of which were correctly predicted, a success rate of 56.2%.
Here are the predictions for last week’s games.

Predictions for Round 3

Here are the predictions for Round 3. The prediction is my estimated expected points difference with a positive margin being a win to the home team, and a negative margin a win to the away team.