后天考试， 今天急问

The following appeared in a letter to the editor of a popular science and technology magazine.

“It is a popular myth that consumers are really benefiting from advances in agricultural technology. Granted — consumers are, on the average, spending a decreasing proportion of their income on food. But consider that the demand for food does not rise in proportion with real income.
                As real income rises, therefore, consumers can be expected to spend a decreasing proportion of their income on food.
                Yet agricultural technology is credited with having made our lives better.”

谁能给我整理一下这个题的逻辑思路是什么啊?

还有就是逻辑错误都是什么？先谢谢大家了，后天就要考试了

原观点：因为食品消费占收入比重逐渐降低，所以农业技术改善了生活。

作者观点：原观点错，因为食品需求与收入并不同步增长，所以当收入增加时，该比重会自然降低，而不归功于农业技术

逻辑错误：1. food demand不等于food expenses，还有价格等因素

2. 收入增长与比率降低，不一定有因果关系

只想到这么两条