select t1.pay_ability
,concat(truncate(sum(case when coalesce(overdue_days,0)>0 then 1 else 0 end)/count(*)*100,1),'%') as overdue_ratio
from loan_tb t
join customer_tb t1 on t.customer_id=t1.customer_id
group by t1.pay_ability
order by overdue_ratio desc