I'm not sure I understand the logic behind how they set the yields on their CDs.
Here are the rates that Ally Bank are currently offering
Savings 1.05%
3 month - $5000 0.30%, $5000-25000 0.34%, $25,000+ 0.39%
6 month - $5000 0.60%, $5000-25000 0.63%, $25,000+ 0.67%
9 month - $5000 1.00%...