1st one has been answered !!!!
2. For a long time,the Pareto law has lumbered the economic scene like erratic blocks on the landscape.
lumbered is as the gentlemen above me already said has a negative meaning
in the context it can mean the Pareto laws has turned the economy into a shallow, senseless/meaningless , boring, obstructing etc . just like erratic rocks on the landscape (just like the big rocks standing tall , obstructing/ hampering the the surroundings )