Plutocracy, defines a society or a system ruled and dominated by the small minority of the wealthiest citizens. Is this what we have in USA or Democracy?

For reference check out the charts attached here which are by Organization for Economic Co-operation and Development (OECD) using the World Top
Incomes Database, which charts shows how income gains between 1975 and 2007 were divvied up in 18 OECD countries for which the researchers had data. Nowhere did the rich benefit as much as in USA.

As you can see, in some countries like Denmark the vast majority of income gains went to the bottom 90
percent -- SOCIALISTS! -- while nearly half of U.S. income gains went to the richest one percent -- under the slogan that this is "freedom baby".

And of course ultimate example of the above facts is that while all OECD countries have Government run Universal Socialized Health Care (NHS) as a result of which all their People get health care for FREE for Taxes they pay USA does not have this as a result of which 2-Million+ Americans go bankrupt per Year due to health care cost!

Some great related articles being:
http://www.realnewspost.com/sa.php?a=64892
&
http://www.huffingtonpost.com/2014/05/01/income-inequality-charts_n_5241586.html

So what do you think: Is USA a Democracy or a Plutocracy?
And if Plutocracy as facts show it to be, how do we change things for better?