4 ms·

> the Web went from 46% encrypted page loads to 67% according to statistics from Mozilla - a gain of 21% in a single year No no no... That's a gain of 50% (giv

> the Web went from 46% encrypted page loads to 67% according to statistics from Mozilla - a gain of 21% in a single year No no no... That's a gain of 50% (give or take) or 21 percentage points; not a gain of 21%.

gmac 9y ago
The broader problem is that expressing changes as percentages is often intrinsically ambiguous. I'm not sure that the way you're choosing to signal the difference is widely appreciated or understood.
- Shoothe 9y ago
  It depends on what do you mean by "widely understood". People that deal with numbers know the difference, but other can just read Wikipedia, see https://en.wikipedia.org/wiki/Percentage_point https://en.wikipedia.org/wiki/Percentage_point It may be similar to people not feeling the difference between causation and correlation.
  - JorgeGT 9y ago
    It is a common mistake, I remember that not so long ago my government (Spain) had to amend a law because the initial text incorrectly said % instead of percentage points.
bufferoverflow 9y ago
Why are you calculating the gain out of 46% and not out of 100%? It clearly doesn't talk about the gain of a percent of a percentage.
- chairmanwow 9y ago
  Percentage changes are a scaling factor against the previous number. 1-(new/old) is how it should be calculated. So even though they are comparing two percentages, they can't directly subtract them (new - old). Percentages describe _relative_ change.
stdbrouw 9y ago
Unlike with e.g. prices, the sum total of all web traffic provides a natural ceiling, so new/old (multiplicative) and new/total (additive) are both defensible.
- dkersten 9y ago
  Sure, but you need to be clear about what you're representing. Saying X% implies (because of the % sign and what percentages are...) that its multiplicative while percentage points implies additive (and the article used the %, which made it sound multiplicative, but in reality used the additive value -- lots of confusion!)
alkonaut 9y ago
People often (incorrectly) use "%" instead of writing out "percentage points". Percentage points increase is the correct figure to use here I think, it's more informative to state that the increase is 21 percentage points than that the improvement is ~50%.
jaas 9y ago
Good point, thanks. We just pushed a fix for that language, should show up live shortly.

gmac 9y ago

The broader problem is that expressing changes as percentages is often intrinsically ambiguous. I'm not sure that the way you're choosing to signal the difference is widely appreciated or understood.

Shoothe 9y ago
It depends on what do you mean by "widely understood". People that deal with numbers know the difference, but other can just read Wikipedia, see https://en.wikipedia.org/wiki/Percentage_point https://en.wikipedia.org/wiki/Percentage_point It may be similar to people not feeling the difference between causation and correlation.
- JorgeGT 9y ago
  It is a common mistake, I remember that not so long ago my government (Spain) had to amend a law because the initial text incorrectly said % instead of percentage points.

bufferoverflow 9y ago

Why are you calculating the gain out of 46% and not out of 100%? It clearly doesn't talk about the gain of a percent of a percentage.

chairmanwow 9y ago
Percentage changes are a scaling factor against the previous number. 1-(new/old) is how it should be calculated. So even though they are comparing two percentages, they can't directly subtract them (new - old). Percentages describe _relative_ change.

stdbrouw 9y ago

Unlike with e.g. prices, the sum total of all web traffic provides a natural ceiling, so new/old (multiplicative) and new/total (additive) are both defensible.

dkersten 9y ago
Sure, but you need to be clear about what you're representing. Saying X% implies (because of the % sign and what percentages are...) that its multiplicative while percentage points implies additive (and the article used the %, which made it sound multiplicative, but in reality used the additive value -- lots of confusion!)

alkonaut 9y ago

People often (incorrectly) use "%" instead of writing out "percentage points". Percentage points increase is the correct figure to use here I think, it's more informative to state that the increase is 21 percentage points than that the improvement is ~50%.

jaas 9y ago

Good point, thanks. We just pushed a fix for that language, should show up live shortly.