Measure in line chart problem

I have a hospital finance data set including the financial information (like net income etc.) for each hospital from 2011 to 2019. I am now creaing a line chart to show the net income by year for the selected hospital, and I want to add the average netincome for all the hospital by year into the chart. I am trying to use a measure average(net income) but when I add this into the chart it gives me a horizental line.. how can I make this average net income change by year in the chart? 

Thanks for any advice!

PS:

There are 5 columns in the data, Hospital ID, Hospital Name, Year, Attribution, Value

Where the Attribution include different benchmark name like Net income, Operating revenue etc. and the Value column shows the exact number for the corresponding attribution.