When i run my code i get the issue column s.popchage2000 does not exist. please help

```
select name,
       SUM(population_2010 - population_2000) as popchage2000,
       SUM(population_1950 - population_1900) as popchange1900
from states as s
where s.popchage2000 > s.popchange1900
group by name;

```