From Think Progress:
...close to a million federal workers performing tasks that are deemed non-essential could be furloughed, leading to delays and shutdowns in the following services:
FINANCIAL SERVICES. The Small Business Administration will stop making loans, federal home loan guarantees will likely go on hold, and students applying for financial aid could also see delays and backlogs in applications.ARMED FORCES. U.S. troops serving at home and abroad could stop receiving paychecks if the shutdown continues for an extended period and changes of station would also be delayed and facility and weapons maintenance would be suspended. Families back home would also be impacted.HEALTH CARE. The National Institutes of Health will stop accepting new patients and delay or stop clinical trials. Medicare and the Veterans administration will continue paying out benefits, but new filers could face delays and doctors and hospitals may also have to wait for reimbursements.PUBLIC SAFETY. The Environmental Protection Agency would stop reviewing environmental impact statements and food inspectors would stop conducting workplace inspections unless there is an imminent danger. The Bureau of Alcohol, Tobacco, and Firearms could stop processing applications for permits.SECURITY AND TRAVEL. The Department of Homeland Security would suspend the E-Verify program, which helps businesses determine the eligibility of employees, creating hiring delays. The State Department will also likely halt new passport and visa applications.
All this will come at a price. The last two shutdowns during the Clinton era — one lasted six days in 1995 and another stretched 21 days at the end of 1995 and beginning of 1996 — cost the country 0.5 percentage points of gross domestic product (GDP) growth and more than $2 billion (in today’s dollars) in unnecessary expenses — as government employees abandoned their jobs to prepare for the shutdown. Economists estimate that were a short-term shutdown to occur next month, it “would do significant economic damage, reducing real GDP by 1.4 percentage points.” A two-month shutdown could “precipitate another recession.”