问题 多项选择题

下面哪些物品的需求相对来说是缺乏弹性的()。

A.水

B.电

C.奢侈品

D.煤气

答案

参考答案:A, B, D

解析:不同的物品对价格变动的反映程度会不同,经济学上称之为供需的价格弹性。如果一种物品的需求对价格变化的反应大,可以说这种物品的需求是富有弹性的;反之如果对价格变化反应不大,则是缺乏弹性,或者说是趋于刚性的。通常,生活必需品倾向于刚性,非必需品及奢侈品倾向于弹性。城市中的基础设施如水、电、煤气作为生活必需品,其需求相对来说是缺乏弹性的。一个特殊的例子是土地,短期内城市土地的供应是接近刚性的,土地供应曲线呈垂直向上的直线。但是从中、长期来看,土地的供给仍呈弹性。

单项选择题

Malthusian fears that population growth will outstrip food supplies have been widely discounted as food production has kept well ahead of growing human numbers in the last half century. While population doubled, food supply tripled, and life expectancy increased from 46 in the 1950s to around 65 today. But more recently, some experts have once again been sounding the alarm about a possible food crisis.

The reason lies in the combined impact of many factors including climate change, forest denudation, land degradation, water shortage, declining oil supplies, species extinction, destruction of coastal ecosystems and the growing demands for a meat-rich diet from newly developed parts of the world.

At the root of all these problems has been the ruthless exploitation of the earth’s resources, fuelled by growing affluence in some parts of the world and desperate poverty in others. Between 1980 and 2000, global population rose from 4.4 billion to 6.1 billion, while food production increased 50 per cent. By 2050, the population is expected to reach 9 billion.

Data shows that while grain yields per acre have been increasing, the rate of increase has been slowing since the days of the Green Revolution in the 1970s. Most of the benefits of irrigation, machinery, fertilizer and plant breeding have already been realized. The production of grain per acre is close to the maximum obtainable through photosynthesis.

To keep up with the growth in human population, more food will have to be produced over the next 50 years than has been during the past 10,000 years combined, said the participants of the recent UN-backed forum in Iceland on sustainable development. It is, of course, possible that new technologies, smart environmental management and sensitive social policies will combine to good effect to usher in a new green revolution. But as grain reserves have fallen to their lowest level for many years, this cannot be guaranteed.

At the 1996 World Food Summit political leaders from 186 countries pledged to halve the number of hungry people in the world by the year 2015, or a reduction of 20 million each year. At that time, about 800 million people were reported to suffer from under- nourishment. In 2007 estimates from the UN Food and Agriculture Organization (FAO) suggest that there are 854 million people who do not get enough to eat every day. "Far from decreasing, the number of hungry people in the world is currently increasing," said FAO Director-General Jacques Diouf. (Of course, world population has increased by some 800 million in that time, so food supplies have kept up relatively well, but have failed to reach an increasing number, let alone reduce the total going hungry.)

What’s the author’s attitude towards Malthusian theory()

A. Mildly supportive

B. Somewhat indifferent

C. A little alarmed

D. Seemingly objective

判断题