> It's still an improvement, i.e., progress.
Perhaps this is a matter of opinion. It's not entirely clear to me that coal miners in 19th-century England were definitely better off, as a group, than their smallholding or even tenant-farming great-grandfathers.
Regardless of what either of us may think, though, I don't know of any statement by Marx that they *were* better off.
Marx, as far as I know, doesn't address this question directly and doesn't seem to have been very interested in it. The whole thrust of the historical parts of the Manifesto, in particular, at least as I read it, is about something quite different -- namely, the way in which each social order hatches or incubates the forces that are destined to destroy it. This for me is perhaps the deepest and most powerful insight that Marx bequesthed us (among many others, of course).
This vision of history seems to me much richer, more detailed, clearer-eyed, and dare I say more scientific, than what Carrol called the "ever-upward" narrative of "progress". More scientific in the sense that Marx actually shows us the *forces* that are at work. The Whig version -- the story of steady incremental improvement -- has no such dynamical component at all, other than a generous gaseous necessity, immanent in human nature or the cosmic order, for things to be getting better all the time, as the song says.