Below is a table showing the killers in every 100 deaths in a city during the last three decades. Look at the graph and write an essay of about 120 words making reference to the following points:
1 ) the distribution of killers in different decades and the general trend in these decades
2 ) the possible reasons for the distribution of these killers in the city
Killers in Every 100 Deaths

Period	Cancer	Heart disease	Traffic Accidents	Other Causes
1970s	2l	16	7	38
1980s	28	26	15	31
1990s	27	27	21	25

The death percentages of different causes in the city during the last three decades have changed significantly．The death percentage by traffic accident has the greatest change from 7% in the l970s to 21% in the1990s，while that of other causes has declined sharply from 38%to 25%． The other killers--cancer and heart disease--have also increased steadily by 6% and ll% respectively．
These changes reflect the development of the city in the last three decades．People travel more than they did three decades a90，because they are more engaged in business activities and social communications now．As a result，traffic accidents increase．With better diet and longer life，diseases like cancer and heart attack become bigger killers than other kinds of diseases．