Republicans in Congress introduced legislation this week that would restrict federal spending to the arbitrary level of 18 percent of gross domestic product. This would require devastating cuts to programs that preserve the social safety net and protect the middle class. It would also make the United States the lowest-spending economically advanced country in the world.

The last time the United States had spending this low was in 1966. Much has changed since then, which makes a federal budget at that level both impractical and undesirable. We are an older country, with more retirees receiving the Social Security and Medicare benefits they’ve earned during their working lives. Social Security benefits have been consciously increased to improve the quality of life for retirees. Health care costs have multiplied so providing Medicare, veterans care, and Medicaid is much more expensive. Education has become more costly, and government fuel costs have risen along with everyone else’s. Just about the only thing that hasn’t changed is our national predilection for catchy pop songs.

We are a very different country than we were back then, with very different needs and with stronger economic competitors making investments in their own countries to make themselves strong. We must match those investments to remain the No. 1 economy and the most competitive nation on earth. We simply can’t put a 1966 transmission into a 2013 Mustang.

Sarah Ayres is a Research Associate at the Center for American Progress. Michael Linden is the Director for Tax and Budget Policy at the Center.