create table t (a date, b float);
insert into t
values
('2022-12-01', null),
('2023-01-01', 0.1),
('2023-02-01', 0.15),
('2023-03-01', 0.5),
('2023-04-01', 0.7),
('2023-05-01', 0.3);
select
a, b,
( 1000 * exp(sum(ln( coalesce(b, 1))) over (order by a)) )::numeric(5, 1) c
from t