Some of the best sources are actually the ones with clear ideological bents because you can filter the whole story knowing where they’re coming from.
Most of the sources used by communist theorists are capitalist rags (Economist has been around for well over a century and has a very clear bias) and industrial magazines (banking, mining, light industry) to understand the positions of the bourgeoisie and then direct interviews and union meeting minutes to understand the positions of the workers.
I like how the upper class response is larger for people making less than $10,000/yr than any other bracket until you hit $150,000