The partial government shutdown will likely deliver a “big negative” to the first jobs report of 2019 and trigger a GDP decline, a senior economic adviser to President Donald Trump said Thursday.

Kevin Hassett, chairman of the White House Council of Economic Advisers, also tried to downplay the effects the shuttering of nine Cabinet departments and other smaller agencies will have on the U.S. economy, including increasingly volatile stock indexes.

“So, what we’ll say if we were to see that negative [jobs impact] number is, ‘Well, sure it was negative this, but if you adjust for the furlough, it looks like another plus-200 month,’” he told reporters outside the West Wing after a television interview.

Hassett also did some back-of-the-envelope math in estimating a partial shutdown through next week would bring down the gross domestic product by about one-tenth its current level.

American stock markets dropped again Thursday morning after Apple reported slower sales due to the Trump administration’s tariffs on China, leading to declined sales there. U.S. and global markets have been on a roller coaster ride lately, with sharp drops and steep comebacks.