After estimating a trend model for annual time-series data,you obtain the following residual plot against time. 
The problem with your model is that
Definitions:
National Unemployment
The percentage of the labor force that is unable to find employment, considered an important indicator of the economic health of a country.
Average Age
The mean age of a specific group or population, calculated by dividing the sum of individual ages by the number of individuals.
U.S. Workforce
refers to the total population of employed and unemployed individuals in the United States, actively participating or seeking participation in the country's labor market.
Management Position Description Questionnaire
A tool used to define the responsibilities, duties, and qualifications required for a management position.
Q2: Referring to Instruction 17-4,which investment has the
Q22: The number of alternatives for the payoff
Q24: Referring to Instruction 14-15,the Holt-Winters method for
Q62: Referring to Instruction 13.25 Model 1,the null
Q76: To avoid the pitfalls of regression,you should
Q98: Referring to Instruction 13.25 Model 1,you can
Q125: Referring to Instruction 13.35,which of the following
Q129: Referring to Instruction 13.17,when the microeconomist used
Q141: Referring to Instruction 13.22,the null hypothesis H<sub>0</sub>:
Q163: Referring to Instruction 12.26,there is no evidence