Please explain this sentence in plain English.
"If reading Piketty reminds us of the troubling inequalities of wealth, reading the recent, pathbreaking OECD report on adult skills in rich countries provides an equally grim picture of the inequalities of knowledge---one that for the United States is terrifying."

--- stands for one-long-hyphen which I don't know how to input.
Piketty is the French economist and author of the 700-page book "Capital in the Twenty-First Century"---argues that free markets tend do produce inequalities of wealth that become dynastic and anti-meritocratic.

Question

Please explain this sentence in plain English.
"If reading Piketty reminds us of the troubling inequalities of wealth, reading the recent, pathbreaking OECD report on adult skills in rich countries provides an equally grim picture of the inequalities of knowledge---one that for the United States is terrifying."

--- stands for one-long-hyphen which I don't know how to input.
Piketty is the French economist and author of the 700-page book "Capital in the Twenty-First Century"---argues that free markets tend do produce inequalities of wealth that become dynastic and anti-meritocratic.

Answer

So, basically, this sentence is comparing two different things: 1. Pikkety's writing. 2. the OECD report.

1. Pikkety = inequalities of wealth

2. OECD report = inequalities of knowledge

The sentence is making the point that these inequalities are EQUALLY BAD or scary.

The "one" in "one that for the US is terrifying" refers to the "picture" -- the "picture of the inequalities of knowledge" (OECD report).

Answer

Piketty (a French economist) wrote that free markets can make inequalities of wealth (ie. some people are much richer than others). He wrote this in a book called "Capital in the Twenty-First Century". He said that these inequalities of wealth eventually become like dynasties (ie. the wealth stays in the same families) and anti-meritocratic (ie. those in power may not be the most qualified to do so).
A recent report states that similar inequalities of knowledge exist (ie. some people are much more knowledgeable than others). This may have terrifying implications for the United States.

Answer

So, I can read the part, like "Grim picture that is terrifying for the United State" right?
Thank you everyone.

Answer

I especially don't get the meaning of "one that for the United States is terrifying"