Rule of thumb from Fidelity: Your retirement savings should be 10x your final income

I just read an interesting article on retirement savings by Andrew Biggs in Forbes.  He discusses the Fidelity rule of having liquid assets of 10x one's final income and drawing down 4.5%/year for life and combining this with a social security calculation to determine retirement income levels.

Here is a table from the article:

For retirees who were earning up to about $120,000 this works out, since "experts" say that one should aim at replacing at least 70% of one final income in retirement.

I liked this approach because it sets a clear and easily-understood goal.

The full article can be found at http://www.forbes.com/sites/andrewbiggs/2016/01/14/more-mistaken-retirement-crisis-claims-this-time-from-fidelity-investments/#2715e4857a0b2853dd162998