Incidence and death rates are standardized by age to the 2000 United States standardmillion population.
发病率及死亡率根据年龄按2000年美国标准百万人口标化。
2
To find out, they tracked 102, 000 Twitter users over six months, analysing the 140-character-or-less text from 129 million of their tweets with standard techniques from psychology.