What is the best way to use Total to get percentage of groups in PostgreSQL

In excel and other similar software you can use total to get the percentage. Can anyone tell what is the most efficient way to replicate total function.

I have used nested query but I am not getting right result

select retpre04recency,
count(*) as CustomerCount,
(select count(*) from extractsummary) as Total,
round(count(*)/(select count(*) from extractsummary),2) as CustomerCount
    from extractsummary
    group by retpre04recency
    order by retpre04recency asc
    ;

My result in percentage column is zero. can anyone help?