of goods and services between countries. The $1 per day level is generally used for the least developedcountries, primarily African; the $2-per-day level is used for middle-income economies such as those of EastAsia and Latin America.Indian Onion#071009The most vital ingredient in Indian cooking, the basic element with which all dishes begin and, normally, thecheapest vegetable available, the pink onion is an essential item in the shopping basket of families of allclasses. A popular saying holds that you will never starve because you can always afford a roti (a piece ofsimple, flat bread) and an onion.But in recent weeks, the onion has started to seem an unaffordable luxury for India's poor. Over the past fewdays, another sharp surge in prices has begun to unsettle the influential urban middle classes. The sudden spikein prices has been caused by large exports to neighboring countries and a shortage of supply. With its capacityfor bringing down governments and scarring political careers, the onion plays an explosive role in Indianpolitics. This week reports of rising onion prices have made front-page news and absorbed the attention of thegoverning elite.Seatbelt #071010I am a cyclist and a motorist. I fasten my seatbelt when I drive and wear a helmet on my bike to reduce the riskof injury. I am convinced that these are prudent safety measures. I have persuaded many friends to wearhelmets on the grounds that transplant surgeons call those without helmets, "donors on wheels”. But a bookon 'Risk’ by my colleague John Adams has made me re-examine my convictions. Adams has completelyundermined my confidence in these apparently sensible precautions. What he has persuasively argued,particularly in relation to seat belts, is that the evidence that they do what they are supposed to do is verysuspect. This is in spite of numerous claims that seat belts save many thousands of lives every year.第55页，共111页
There is remarkable data on the years 1970 and 1978 countries in which the wearing of seat belts is compulsoryhave had on average about 5 per cent more road accident deaths following the introduction of the law. In theUK, road deaths have decreased steadily from about 7,000 a year in 1972 to just over 4,000 in 1989. There is noevidence in the trend for any effect of the seat belt law that was introduced in 1983. Moreover, there isevidence that the number of cyclists and pedestrians killed actually increased by about 10 per cent.Ocean floor#071012The ocean floor is home to many unique communities of plants and animals. Most of these marine ecosystemsare near the water surface, such as the Great Barrier Reef, a 2,000-km long coral formation off the northeasterncoast of Australia. Coral reefs, like nearly all complex living communities, depend on solar energy for growth(photosynthesis). The sun's energy, however, penetrates at most only about 300 m below the surface of thewater. The relatively shallow penetration of solar energy and the sinking of cold, subpolar water combine tomake most of the deep ocean floor a frigid environment with few life forms.