As you know, GAO supports the Congress in meeting its constitutional responsibilities and strives to help improve the performance and accountability of the federal government for the benefit of the American people.
There has been a rapid improvement in the performance of the country. 
mnli hypothesis: There has been a rapid improvement in the performance of the country.  premise: As you know, GAO supports the Congress in meeting its constitutional responsibilities and strives to help improve the performance and accountability of the federal government for the benefit of the American people.