Unless an earmark pays 100% of the costs of something, the earmark is totally an illusion. Even if it does pay 100% of the costs, it is often mostly an illusion.
In practice, most earmarks fall into the former category, and thus are entirely about manipulating the public. Not that I'm necessarily objecting to manipulating the public.
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worked example:
If fuel taxes bring in $100, which is spent on road maintenance, and then topped up by $40 of money from general revenue, that implies that the government thinks that $140 is the point at which marginal benefit drops below marginal cost. In other words, if there was no fuel tax, they'd probably still try to spend $140, or thereabouts. The earmark is entirely illusory.
If fuel taxes bring in $100, which is spent on road maintenance, and is not topped up, then that implies that the government thinks that the point at which marginal benefit drops below marginal cost is some number below $100. If there was no fuel tax, their spending on road maintenance would go down. Go down to what? Let us suppose that it would go down to $60. Then the fuel tax earmark is 40% reality, 60% illusion.
The reality is, roads would be maintained the same way with or without earmarked tax revenue.
Think about it.
Scenario a) X dollars from fuel tax are revenue for federal budget. Federal budget decides whatever it wants to do with the money, but roads require Y dollars for maintenance.
Scenario b) X dollars are earmarked for road maintenance. Federal budget can't do anything else with the money but spent them on road maintenance. Roads require Y dollars for maintenance. X is covered from earmarked revenue, and the difference comes from federal budget.
Did ANYTHING change between scenarios? In both cases taxpayers paid X dollars of fuel tax and Y dollars for road maintenance.
Earmarking tax revenue for a cause that requires greater amount of money and would be covered anyway is just PR mechanism to placate people / opposing party. Opposing party might know it is just illusion but still needs to placate their own constituents.
The goal of this is to create another tax revenue stream without angering your voters. And so we complicate what is relatively simple so that general population thinks the tax is for their benefit. It still is but for a different reasons.
https://www.taxpolicycenter.org/briefing-book/what-highway-t...
I would say that 60% of taxes might be raised for health and education this way.
I suspect that EVs weren't exempted by design, but just slipped through the gap. Australian road tax is applied to petrol/gasoline/diesel. The number of EVs hasn't warranted changing this formula (the alternative being a tax on kms traveled). In Australia, EVs still haven't taken off (as there haven't been any incentives to buy them; in fact as they tend to be expensive, they often fall under the luxury car category and get taxed even more), so there are still very, very few on the road. It's very slowly changing, and this change is definitely looking into the next decade more that the next year, but still strikes me as odd timing - just when momentum is building to EVs, this will dull that momentum (at least without an incentive to _purchase_ an EV.
There are three main reasons for a tax to exist:
1. To bring revenue
2. To create incentive
3. Social justice (or illusion of it)
Revenue from a specific tax is almost never used for a specific purpose. All revenue goes into a large bin from which the government takes to finance everything.
Revenue from fuel/road tax is not used to finance building roads. Infrastructure is financed from budget or by private companies who then can impose tolls on road users.
Fuel tax (besides obvious goal of creating revenue) is there to create incentive to drive less and to drive more efficiently (using less fuel). This is not to preserve roads but rather to preserve capacity and environment.
I can only assume that tax on electric vehicles is as a response to increasing use of EVs. Initially, EVs were exempted from taxes to create incentive to use them more. Now that it is pretty clear EVs took off and will be widespread no matter what, some countries start to remove those exemptions to ensure continuing revenue stream.