Suppliers are finding that they have to stay open, too, to keep their customers' factories humming.

On the way up, factories hummed, corporate profits rose and stock prices followed along happily.

To keep the factories humming and the diplomats employed.

The endless buying and importing has kept factories humming everywhere.

A boom in export sales, aided by the lower value of the dollar, has kept factories humming.

Time passed, the factory hummed, and the robot population grew in number and variety.

The cool and dark factory hummed with activity, but a worker jumped at the chance to show my friend and me around.

Because consumer spending accounts for two-thirds of the nation's economic output, that would do the trick, getting factories humming again.

My little factory was humming along, now, with thirty reconditioned robots at work, each turning out nearly one item per week.

So, for millennia now, we have been locked in this endless war, which serves to keep our population down and our factories humming.