There is already sheet named "DigikeyRateVariances" when you run the sub. 
For Each Sht In Sheets
If Sht.Name = "DigikeyRateVariances" Then ShtExists = True
Next

If Not ShtExists Then Sheets.Add.Name = "DigikeyRateVariances"

Set DKData  Sheets("DigikeyRateVariances")