Fidelity manages its’ budget, in large part, to its forecast of the S&P for the coming year. Mixed in is the general level of interest rates as Fidelity (as with other financial firms) makes good coin in a rising interest rate environment. The business units throughout the company then roll up their forecasts, including hiring expectations, to Abby. Think of Fidelity as the QE2…once it sets sail it can take awhile to maneuver, change course etc…
My best guess is that a number of things (unlike in the 90s and 00s) have conspired to keep employment at Fidelity steady for now: rising rates, boomer retirements continue unabated, thirst for advice continues to grow, and the desire to stay ahead of competitors as far as technology goes. What could change? The S&P could drop to 3200 or less; the Fed cuts rates; customers bail on managed products and/or TOA out.
Well stated point by @ywm+1hTQMQMr.