What does 发达国家占7％，发展中国家占17％ in the textbook 规范教程HSK6上 refer to?

Question

据权威机构统计，除吸烟、遗传等，感染也是引起癌症的重要原因之一。全球癌症17％是由细菌、病毒等感染引起的，但发达国家占7％，发展中国家占17％。造成这种差别的原因是，发达国家能更有效率地防治感染。
_{HSK Coursebook (HSK规范教程) 6上, p.7.}
[Google Translate]: According to statistics from authoritative organizations, in addition to smoking, genetics, etc., infection is also one of the important causes of cancer. 17% of global cancers are caused by infections such as bacteria and viruses, but developed countries account for 7% and developing countries account for 17%. The reason for this difference is that developed countries can prevent infections more efficiently.

I'm trying to understand what the two statistics in bold refer to: 7% of what? 17% of what?

My guess is that it's saying (a) infections cause 17% of global cancers, (b) infections cause 7% of cancers in developing countries, and (c) infections cause 17% of cancers in developed countries. However, this seems mathematically impossible unless there are countries which are neither 发达国家 nor 发展中国家.

Question: What does 发达国家占7％，发展中国家占17％ in the textbook 规范教程HSK6上 refer to?

Answer 1

According to my limited arithmetic capabilities, 7 + 10 = 17, so probably a typo.

As you say, unless there is a category of countries outside of [developed, developing] 全球 should refer to these two categories.

除吸烟、遗传等
apart from smoking and hereditary factors etc.
感染也是引起癌症的重要原因之一。
infection is one of the important causes of cancer.
全球癌症17％是由细菌、病毒等感染引起的，
17% of cancers worldwide are caused by bacterial or viral infections
但发达国家占7％，
however developed nations only account for only 7% of these cases,
发展中国家占10％。
whereas developing nations account for 10% of these cases.

Answer 2

全球癌症17％是由细菌、病毒等感染引起的，但发达国家占7％，发展中国家占17％。

Again, we need to know the full context to understand why this sentence was written this way. Let me try to change a word to make it more clear, but may not fit the tone the writer wanted to deliver.

全球癌症17％是由细菌、病毒等感染引起的，其中发达国家占7％，发展中国家占17％。

Now the sentence is a style of direct reporting the statistics.

It seems the disproportional ratio between the developed countries and the developing countries contradicts another set of data, such as source allocation. The inequality was the focus of the writer, so the use of 但 (but).

Answer 3

1. I think it is clear that the writer is referring to infection-induced cancers specifically, because 发达国家能 更 有效率地防治感染 explains why there is a difference in the prevalence of infection between 发达国家 and 发展中国家, and by extension, the prevalence of infection-induced cancers, and not the overall prevalence.

2. It is possible that there is a third category, 最不发达国家 (least developed countries). From Wiki:

   现今随着经济发展，已有部分的发展中国家转变成发达国家（拉脱维亚、爱沙尼亚、立陶宛、捷克、斯洛伐克、斯洛文尼亚），另外相反的是也有部分的发展中国家反而因生活水平退步而滑入最不发达国家。

Perhaps data were not collected in LDCs? Or the writer omitted the discussion of LDCs deliberately to better contrast developed and developing countries? There is no solid proof, but this should not affect our logical judgment in point 1. In any case, I think the two 17% are just a coincidence.