These are tough times for two big US dollar store chains. In the past month, Family Dollar said it will close nearly 1,000 stores and 99 Cents Only said it will go out of business.

Both companies said inflation and shoplifting have contributed to their troubles. While inflation has pressured the companies’ low-income customer base and shoplifting has squeezed their profits, those factors alone can’t explain their difficulties.

Years of strategic mistakes and underinvestment have plagued Family Dollar and 99 Cents Only, retail analysts say. Both brands were acquired by other companies and faltered under their new owners.