People interested in malthusian theories focus on calories
Which is of course total nonsense, as number of calories consumer per capita varies extremely little over huge differences in GDP. some data
I'm sorry if I wasn't clear, but I reject GDP for this purpose. I suspect that Braudel and the conventional wisdom about 1300 are like saying that people today are as kings, for they have the greatest musicians of the century at their beck and call on youtube. GDP tells how nice are the luxuries, but it doesn't tell if someone is starving.
Malthusians claim that percent of income spent on food is a good inverse predictor of number of calories, that people eat few calories when they can't afford more. GDP, whether in the 13th century or especially in the 20 century can mask this, because what can be bought with the remaining income is quite variable. Greg Clark claims that the poor in England in 1800 were getting 1500 calories per day, which is off the chart you link to.
I can't find him giving calorie estimates for other years, but he and his predecessors Phelps-Brown-Hopkins and Steffens claim that English labor income peaked in 1450, that the black death raised wages in a malthusian manner, in contrast to the claims you quote. This could be special to England or could be a result of measuring wages in necessities (calories), or could be a result of malthusians putting a finger on the scales. (Clark is a malthusian. I don't know about PB, H, or S.)
I can't find him giving calorie estimates for other years, but he and his predecessors Phelps-Brown-Hopkins and Steffens claim that English labor income peaked in 1450, that the black death raised wages in a malthusian manner, in contrast to the claims you quote.
How is it measured? If you use nominal wages, you will see this effect, Malthusian or not, because amount of metal money per capita is inversely proportional to population. You need some sort of GDP estimates to adequately measure wages.
Malthusians claim that percent of income spent on food
D...
This is an attempt to list all of the possible ways in which humanity may avoid scenarios where the average standard of living is close to subsistence, in response to Robin Hanson's recent series of posts on Overcoming Bias, where he argues that such an outcome is likely in the long run.
I'll start with six, some suggested by myself, and others collected from comments on Overcoming Bias and Robin's own posts. If anyone provides additional ideas, I'll add them to the list.
(I have a more general point here, BTW, which is that predicting the far future is very difficult. Before thinking that some outcome is inevitable or highly likely, it's a good idea to repeatedly ask oneself "This is all the ways that I can think of why it may fail to come true. Am I sure that all of them have low probability and that I'm not missing anything?" There may be some scenario with a non-negligible probability that your brain simply overlooked when you first asked it.)
Singleton
A world government or superpower imposes a population control policy over the whole world.
Strong Security
Strong defensive technologies and doctrines (such as Mutually Assured Destruction) allow nations, communities, and maybe tribes and families to unilaterally limit their populations within their own borders, while holding off hordes of would-be invaders and immigrants.
Non-Human Capital
Maximizing the wealth and power of a nation requires an optimal mix of human and non-human capital. Nations that fail to adopt population controls find their relative wealth and power fade over time as their mixes deviate from the optimum (i.e., they find themselves spending too much resources on raising humans, and not enough on building machines), and either move to correct this or are taken over by stronger powers. (I believe that historically this was the reason China adopted its one-child policy.)
Unlimited Growth
We don't completely understand the laws of physics, nor the nature of value. There turns out to be some way for economic growth to continue without limit. (Robin himself once wrote "I know of no law limiting economic value per atom" but apparently changed his mind later.)
Selfish Memes
Memes that manage to divert people's resources away from biological reproduction and towards memetic reproduction will have an advantage over memes that don't. On the other hand, genes that manage to block such memes will have an advantage over genes that don't. Memes manage to keep the upper hand in this struggle (or periodically regain the upper hand).
Disease, Warfare, Natural Disasters, Aliens, Keeper of the Simulation
One or more of these come along regularly to keep the human population in check and per capita incomes above subsistence.