The great economist Joseph Schumpeter believed that people are fallible creatures. Because of our fallibility, even the scientific method isn’t entirely objective. Ideology is reflected in, say, a scientist’s (or an economist’s) choice to research one topic instead of another, or the patterns they find (or miss) while interpreting the data:
It embodies the picture of things as we see them, and wherever there is any possible motive for wishing to see them in a given rather than another light, the way in which we see things can hardly be distinguished from the way we wish to see them.
–Joseph Schumpeter, History of Economic Analysis, p. 42