Is the Hubble Sphere Growing?

The Hubble sphere can grow to encompass things that were once moving away from us faster than the speed of light. It can find photons, which were once in superluminally receding regions and put them inside the Hubble sphere so that we can now see them. In physical units where you're like trotting out a ruler to measure things, the Hubble sphere always just grows. So it's growing because the universe is expanding? Or does it have its own kind of growth rate? "It has its own growth rate," he says.