For the sixth straight year IRS tax audits have been declining and have set a new 15 low in 2017 according to the Wall Street Journal. The year, 2010 was their peak, and since then they have lost a third of their enforcement staff.
As the above chart shows, the higher income have seen the biggest decline in percentage of returns audited.
Since 2010, IRS funding is down 8% while tax returns have grown 5%.
You can read more about the decline in IRS tax audits here.