>Using this paradigm, when a conversion rate increases from 14.5% to 18.6%, you would say it increased by 4.1%
No you cannot say it increased by 4.1% and that's because you are talking about per cent. I don't know why you would ever use 4.1% in this context. It is simply wrong.
May be you can say 4.1 percentage points but I don't see a need for it when you can say (and be right) that it increased by 28%.
To be sure, the fact that we are talking about percent changes something, which is what I spent several paragraphs exploring.
To say that subtraction of percentages is against the rules, (while perfectly valid and often used in other units) but percentages of percentages is not against the rules, requires a bit more than "It is simply wrong", don't you think?
Sure, you're "right", when you say it increased by 28%. The point is, perhaps you shouldn't be "right", and what is "right", anyway, if nobody knows what the hell you're really saying?
We see this when talking about tax changes. If somebody wants to minimize the sticker shock of a tax increase, they use the delta. So, if the rate rises from 3% to 4.5%, they say they increased the rate 1.5%. If you want to maximize the sticker shock, you say that the tax rate was increased 50%. Either side can say they are doing the math "right".
Those who care about actually conveying the information, rather than produce sticker shock of either sort, always have to spell it out carefully, by actually saying, "the tax rose from a rate of 3% to a rate of 4.5%" This is a bit longer, but it's necessary, given this weird unit.
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>Using this paradigm, when a conversion rate increases from 14.5% to 18.6%, you would say it increased by 4.1%
No you cannot say it increased by 4.1% and that's because you are talking about per cent. I don't know why you would ever use 4.1% in this context. It is simply wrong.
May be you can say 4.1 percentage points but I don't see a need for it when you can say (and be right) that it increased by 28%.
I believe your logic is backwards.
To be sure, the fact that we are talking about percent changes something, which is what I spent several paragraphs exploring.
To say that subtraction of percentages is against the rules, (while perfectly valid and often used in other units) but percentages of percentages is not against the rules, requires a bit more than "It is simply wrong", don't you think?
Sure, you're "right", when you say it increased by 28%. The point is, perhaps you shouldn't be "right", and what is "right", anyway, if nobody knows what the hell you're really saying?
We see this when talking about tax changes. If somebody wants to minimize the sticker shock of a tax increase, they use the delta. So, if the rate rises from 3% to 4.5%, they say they increased the rate 1.5%. If you want to maximize the sticker shock, you say that the tax rate was increased 50%. Either side can say they are doing the math "right".
Those who care about actually conveying the information, rather than produce sticker shock of either sort, always have to spell it out carefully, by actually saying, "the tax rose from a rate of 3% to a rate of 4.5%" This is a bit longer, but it's necessary, given this weird unit.