Ah, yes - but - when there is a remarkable consistency in the direction of the deviation, one must assume a common external influence is at work. In the case of our economy, one might reasonably expect that perceptions would vary (by orders of magnitude inversely proportional to sample size) in both directions; positive and negative. What we see though, is a consistent negative bias, which is a fair description, as it turns out, for the influence of the mainstream media in shaping people's opinions about the economy, and about much else as well.
While I agree with what I believe to be your bottom line (negative MSM coverage as a causation), I'm not sure I agree that one must assume a (presumably single) common influence is at work. There may be more than one that cause a bias in a common, here negative, direction, but for different reasons.
Some might be influenced by gasoline and / or diesel prices. Others, such as in my area of the country, by spikes in property insurance. Still others by increases in the costs of medical care. And yet others influenced by downward pressures in wages in their occupational group by an overwhelming influx of illegal alien workers, such as drywallers. In short, I believe that multiple causes are as credible an explanation as is a single cause. More probably, we are both correct - it is all of the above.