19. Recent social changes in the country of Spiessa lead the author to predict a continued surge in growth of that country s restaurant industry. Rising personal incomes, additional leisure time, an increase in single-person households, and greater interest in gourmet food are cited as the main reasons for this optimistic outlook. All of these factors are indeed relevant to growth in the restaurant industry. so the prediction appears reasonable on its face. However, three questionable assumptions operative in this argument bear close examination.来源：考试大
The first dubious assumption is that the supply of restaurants in Spiessa will continue to grow at the same rate as in the recent past. However, even in the most favorable conditions and the best of economic times there are just so many restaurants that a given population can accommodate and sustain. It is possible that the demand for restaurants has already been met by the unprecedented growth of the past decade, in which case the recent social changes will have little impact on the growth of the restaurant industry.
A second assumption is that the economic and social circumstances cited by the author will actually result in more people eating out at restaurants. This assumption is unwarranted, however. For example, increased leisure time may just as likely result in more people spending more time cooking gourmet meals in their own homes. Also, single people may actually be more likely than married people to eat at home than to go out for meals. Finally, people may choose to spend their additional income in other ways—on expensive cars, travel, or larger homes.
A third poor assumption is that, even assuming people in Spiessa will choose to spend more time and money eating out, no extrinsic factors will stifle this demand. This assumption is unwarranted. Any number of extrinsic factors—such as a downturn in the general economy or significant layoffs at Spiessa s largest businesses—may stall the current restaurant surge. Moreover, the argument fails to specify the "social changes" that have led to the current economic boom. If it turnsout these changes are politically driven, then the surge may very well reverse if political power changes hands.来源：考试大
In conclusion, this argument unfairly assumes a predictable future course for both supply and demand. To strengthen the argument, the author must at the very least show that demand for new restaurants has not yet been exhausted, that Spiessa can accommodate new restaurants well into the future, and that the people of Spiessa actually want to eat out more.