Firstly, two groups – ideas and thing. Ideas

Firstly, author
explained that we can find reasons of growth of economy by analyzing actions of
country during the certain period of time. Also, he said that all economists
often make an accent on certain parts of economy, whereas it is better to look
at the economy as whole, in order to understand how economy is functioning and
then analyze it step by step. For example, when people look at the machine,
they divide it into two parts – left and right, while they should first look at
the condition of machine and then deepen. 
Further, author discussed about neoclassical theory of growth and new
theory of growth. In his mind, neoclassical theory of growth states that
everything works well and technologies are public goods, whereas in real life
it wasn’t true. The main thing in new growth theory was that inputs of
production can be divided into two groups – ideas and thing. Ideas are
non-rival good and they can be sold as well as things – rival goods. Using
ideas and things it can be explained how economy growth. Then, author just
explained why America’s economy grew and why it was growing relatively faster
than others. There are several reasons. One of them is that from the beginning
USA had a lot of resources and they used them in the right way. Also, America’s
population was growing well. Moreover, they had a technological progress and
progress in infrastructure of country (railways, logistic). Many authors
explained reasons why America was better than others – scale effect,
relationships with other countries and etc. There is no doubt that US economy in
some aspects was worse than some countries – production of metals was lower
than in Britain. However, in general, it became a leader in most industries.  Finally, author concludes that there were a
lot of different inventions and the scale effect was not the main thing.
However, scientists will explain the reasons of growth and why was it first in
America only when theories will blend with conclusions and evidence.