Optimale Steuern, progressive Steuern & Glück

Sollen Reiche mehr steuern zahlen oder einen Grenzsteuersatz von 0% haben? Diese Frage ist nicht esoterisch und auch nicht so trivial wie es zuerst scheinen mag.

In der Volkswirtschaftslehre gibt einen ganzen Zweig der Theorie, die sich mit der Frage befasst, wie die Verzerrungen und Ineffizienzen der Besteuerung möglichst gering gehalten werden können. Das ist die Optimalsteuertheorie, für welche James Mirrlees einen Nobelpreis bekommen hat. Insgesamt sagt die Optimalsteuertheorie, dass Konsumsteuern Einkommenssteuern aus dem Grund vorzuziehen sind weil sie weniger Effekte auf die Arbeitsanreize haben.

Bei der Einkommenssteuer hängt vieles davon ab, welche Annahmen getroffen worden sind. Allerdings lautet ein grundlegendes Ergebnis - wenn Menschen sich nur in ihrer Produktivität unterscheiden - dass der Grenzsteuersatz für Höchstverdiener 0% sein sollte. Im ersten Moment paradox. Aber Durchschnittssteuern sind nicht Grenzsteuersätze. In der Realität unterscheiden sich Menschen sich in mehr als nur Produktivitäten. Und gerade darum geht es in der Diskussion in den USA. Wie wichtig sind Glück und Zufall oder Talent und Leistung für die Erzielung hoher Einkommen? Dies beantwortet letztlich die Frage die Schellhorn so bewegt, nämlich, ob progressive Steuern leistungsfeindlich sind. Dennoch bin ich überzeugt, dass diese Literatur uns dennoch mitteilt, dass Umverteilung nicht hohe Grenzsteuersätze braucht, diese sogar kontraproduktiv sind. Doch das ist ein anderes Thema ... Zurück zu den USA.

Robert Frank schreibt in der New York Times:

Contrary to what many parents tell their children, talent and hard work are neither necessary nor sufficient for economic success. It helps to be talented and hard-working, of course, yet some people enjoy spectacular success despite having neither attribute. (Lip-synching members of boy bands? Money managers who bet clients’ retirement savings on subprime-mortgage-backed securities?)

Far more numerous are talented people who work very hard, only to achieve modest earnings. There are hundreds of them for every skilled, perseverant person who strikes it rich — disparities that often stem from random events.

Und im Jahr 2001 hat Hal Varian - derzeit Chefökonom bei Google - folgendes zum selben Thema geschrieben (hat tip to Mark Thoma):

In the simplest version of the Mirrlees model, taxpayers differ only in their ability: how much they can produce with a given amount of effort. One striking result of this model is that those at the very top of the income scale should face low marginal rates.

This result emerges from a detailed mathematical analysis, but the intuition is not hard to explain. Let us assume, for the sake of argument, that Bill Gates made $1 billion in 2000, an amount larger than any other American taxpayer. Suppose further that despite the best efforts of his accountants, he ended up paying 40 cents of the last dollar he earned to the Internal Revenue Service. Consider the following thought experiment: drop the marginal tax rate from 40 percent to zero for all incomes above a billion dollars. The I.R.S. won't lose any revenue from this reduction, since no one has an income larger than $1 billion. And who knows -- the lower marginal rate might encourage Mr. Gates to work a little harder in 2001, producing new products that would make him, and the rest of us, better off.

Of course, the fact that it pays to reduce the marginal tax rate for billionaires doesn't say much about what tax rates should be like for mere millionaires, a point that has been emphasized by Professor Mirrlees himself and confirmed by subsequent researchers, like Peter Diamond of the Massachusetts Institute of Technology and Emmanuel Saez of Harvard. But the intuitive argument presented above is pretty compelling: if income depends only on ability, those at the very top of the income-ability distribution should face low marginal tax rates.

But perhaps this model is too simple. One might well argue that Mr. Gates, as productive as he is, doesn't owe his success entirely to ability: there was a lot of luck involved, too. And, if truth be told, that's probably true even for mere millionaires.

So let's consider a different model: one in which differences in income are a result only of luck and have nothing to do with ability. In this case, the optimal income tax may well involve taxing billionaires at very high marginal rates. True, aspiring billionaires won't work quite as hard, since the after-tax reward from hitting $1 billion has been reduced. But the chances of becoming a billionaire are pretty low anyway, so taxing billionaires at a high rate won't really discourage much effort by those hoping to become one.

Thus a model where luck is the driving force tends to yield a more progressive optimal tax than a model where ability is the driving force. This is about as far as theory can take us, but it highlights the critical question: How much income results from ability and how much from luck?

(...)

A Harvard social policy professor, Christopher Jencks, and his collaborators pointed out many years ago that income inequality among brothers, who share similar genetic and environmental characteristics, is almost as great as for the population as a whole. This suggests that luck is an important factor in the long run as well.

If luck plays a substantial role in the determination of income, it makes sense to have a progressive income tax, creating a form of social insurance in which the lucky subsidize the unlucky. Perhaps the folk singer Phil Ochs had the best answer for why the upper half of the income distribution should pay so much more in taxes than the lower half: ''And there but for fortune, may go you or I.''

Und weil ein Bildungssystem nicht nur das Talent sondern auch das Glück beeinflussen kann - was wäre gewesen wenn Bill Gates nicht in Stanford sein Studium abgebrochen hätte sondern an der University of North Dakota oder an der TU Graz - wissen wir jetzt warum bestimmte Gruppen in Österreich gegen eine vernünftige Bildungsreform sind. Denn selbst wenn die Normalverteilung für Fähigkeitengelten würde, hat die frühe Selektion im österreichischen Schulsystem eher die Eigenschaft nach den Eigenschaften der Eltern als dem Talent des Kindes zu selektieren. So ein Glück aber auch.