As an alternative, split your money 50-50 between 1 yr and the term that gets you the highest rate. Next year, you've got half of your money, and--if rates have increased a lot, you can do an early sunset (with some penalty) on the longer term and repeat.
Example: If my annual expenses will be $2,000, I put $2,000 in a 1-year, and $2,000 in a five year. Next year, my $2,000 1-year CD comes clear, and I've saved another year worth of expenses, so I do the same thing, building the back of the ladder with my new savings while rolling the initial 1-year CD forward another year. Two years from now, I've got $2,000 in new savings, $2,000 in money from the 1-year (plus $10 interest), and a nice rate locked in for either 3- or 4-year term.