How difficult is this text?

The keywords of the Oxford 3000™ have been carefully selected by language experts and experienced teachers as words which students should know and study because of their importance and usefulness.

To find out which words in a text are part of the Oxford 3000, type or paste it into the box, then click ‘submit’. The words which are not part of the Oxford 3000 will be highlighted in red. The Text Checker will also tell you what percentage (%) of the words in your text are part of the Oxford 3000. You can use this information to judge the difficulty of a text. In general, the more words highlighted in red, the more difficult the text.

In a lower intermediate text nearly 100% of the words will be Oxford 3000 keywords.

In an upper intermediate text 90-95% of the words will be Oxford 3000 keywords.

In an advanced text 75-90% of the words will be Oxford 3000 keywords.

http://oald8.oxfordlearnersdictionaries.com/oxford3000/oxford_3000_profiler.html