> My point is that he hasn't given any reason to think that tax / person really is a better statistic for any purpose.

It's valuable to look at different statistics in metrics in most endeavors. No statistics are perfect, but it's good to check out different ones. Take baseball, for instance. You have batting average (the percent of times a hitter gets a hit) and you have runs scored (runs are baseball's equivalent of "points" or "goals" for people unfamiliar; you win by having more runs than your opponent). The usual way people look at tax burden is looking at percent of GDP - batting average, so to speak. But it's also worthwhile to look at runs scored.

Why is that? Well, maybe batting average isn't the only way to win games. Baseball used to be obsessed with batting average, but neglected a more subtle and advanced statistic called "on base percentage" for years. If you did an analysis of runs scored, you'd find you need on base percentage more than batting average. If you did an analysis of taxation that showed that you could have higher tax yields without taxing a higher percentage of GDP, that'd be well worth knowing.

At the very least, it's a number worth looking at.

> Perhaps it's something like this.... so demotivation is, so to speak, a function of income; so to measure how demotivated our workers are by tax we should look at their taxes in absolute terms.

Actually, the largest reason taxes reduce GDP isn't motivation. It's that the government doesn't invest in the same thing as individuals. When you take taxes from, say, Sergey Brin, and put them under the control of the Senate, that money is going to be spent differently. Brin's money is far more likely to grow the GDP of the United States for the future than whatever the Senate spends it on. The Senate funds some things that produce returns (quality infrastructure, science), some things that help maintain things (a bit of law enforcement, courts), and then a lot of things that don't produce returns. Individuals reinvest in productive endeavors at a much greater rate. Taxation moves resources from the control of people who are more interested in reinvesting and growing their investments to politicians, who are primarily interested in getting re-elected.

> the purpose of taxation is to provide the people with benefits

The purpose of taxation is to increase the revenues that the taxing authority collects. How those revenues are spent are up to the authority. Some governments provide benefits to the people, some buy weapons and try to take over their neighbors, some just steal the money outright. Taxation is sold as providing benefits to the people, but that's not necessarily how the tax yields are spent.

> 1... 2... 3... 4...

I agree with some of those arguments, disagree with others. But the main point is he's not offering a Swiss Army Knife that measures everything, he's just pointing out another number we can look at and take into consideration. To go back to baseball, it's good to look at batting average, on base percentage, isolated power, runs scored, pitches taken, and a number of other factors - there's some great players that have a low average and low on base, but hit with lots of power so they're good. All things being equal, you'd like to have your players take more pitches and wear the other side out. There's a hidden value in a player that takes 1 extra pitch per appearance even if he's just an average player - he'll take 4-5 extra pitches a game, which might mean wearing the opposing pitcher out who has to be taken out. That means your teammate will face a worse pitcher. If you can get a full team of players that take a lot of pitches, you might see spend 10% of the game facing the opposing team's worse reliever when the guy who started the game gets tired and has to be taken out very early.

But if you said - "let's only look at pitches taken", you'd be crazy, because it's useless by itself. If you said, "let's only look at runs scored" you'd be crazy, because it's also about how your teammates do after you get on. But that doesn't mean you should only look at batting average either - or you won't have a complete picture. It's worth looking at all the numbers, so I'm happy this number was brought up for thinking about.