pareto principle coeffiecient

pareto_coef.py

def pareto_coef(data, is_already_sorted = False):
  """https://en.wikipedia.org/wiki/Pareto_principle"""
    if not is_already_sorted:
        data.sort(reverse=True)
    data_len = len(data)
    data_sum = sum(data)
    acum = 0
    for i, value in enumerate(data,1):
        acum += value
        i_pct = 100*i/data_len
        acum_val_pct = 100*acum/data_sum
        if i_pct > 100-acum_val_pct:
            break
    return i_pct

t.sql

DROP TABLE IF exists #data 
go
select count(1) as cnt into #data from SOMETABLE
group by SOME, GROUP, OF, FIELDS
order by 1 desc 

declare @total_cnt bigint 
declare @total_rownumber bigint 
select @total_cnt = sum(cnt), @t_rn = count(cnt) from #data
select top 1 rn_percent  as beer_law_coef  from (
select 
100*ROW_NUMBER ( ) over ( order by cnt desc) / (@total_rownumber*1.0) as rn_percent,
100*(1-sum(cnt) over ( order by cnt desc ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)/(@total_cnt*1.0)) as value_percent
from #data  ) t
where rn_percent >= value_percent