Sum of bottom 20% values

[arnabmit]

I was trying to get the sum of the bottom 20% values, then show it by year. However, the DAX returned the total value.

Bottom 20% Values =
VAR BV = ROUND(COUNTROWS(Sheet1) * 0.2,0)
VAR DR = RANKX(ALL(Sheet1),CALCULATE(SUM(Sheet1[Value])),,DESC,Skip)
RETURN
IF(DR <= BV, CALCULATE(SUM(Sheet1[Value])),BLANK())

Then as per some suggestion, I introduced another set of iterators. This time, it returned the sum of bottom 20%. However, it still was not working properly when trying to group by years.

Bottom 20% Values =
VAR BV = ROUND(COUNTROWS(ALL('Sheet')) * 0.2,0)

RETURN
SUMX(
    'Sheet',
    VAR DR = RANKX(ALL('Sheet'),CALCULATE(SUM('Sheet'[Value])),,ASC,Skip)
    RETURN IF(DR<=BV,'Sheet'[Value],0)
)

For example, if I am trying to check for say 60% instead of 20%, and group them by year, The ranking is not working for the group, but the entire range.

Can anyone please help me understand what I am doing wrong? Thanks in advance!

PBIX