Sentence Correction (SC) | Re: Economic theory fails to explain the extent to which

Economic theory fails to explain theextent to which savings from personal income has shifted to short term bonds, money-market funds, and other near term investments by the instability in the futures market.

1. to which savings from personal income has shifted
2. of savings from personal income that has been shifted
3. of savings from personal income shifting
4. to which savings from personal income have shifted
5. to which savings from personal income have been shifted

I feel the answer must