His remark appeared to be an inarticulate reference to immigrants' fertility rates, which data show are higher than native-born Americans.
"Immigrants create far more businesses than native-born Americans over the last 20 years. Immigrants are more fertile, and they love families, and they have more intact families, and they bring a younger population. Immigrants create an engine of economic prosperity," Bush said at the annual Faith and Freedom conference in the nation's capital.
He prefaced his remarks with an analysis of America's demographic struggles, saying that the rate of Americans entering retirement couldn't be sustained by the current size of the workforce. Economists have long warned that government programs for seniors like Social Security and Medicare face long-term funding problems.
Last year, trustees projected Social Security could pay promised benefits in full through 2036, after which the program could only afford to pay 77% of them. Social Security has already begun paying out more in benefits than it takes in from workers' payroll taxes.
Bush argued Friday the problem lay in an imbalance between working Americans paying taxes and the number of older Americans – living longer – who have been promised government support in their retirement.
"We're going to have fewer workers taking care of a larger number of people the country has a social contract with to be able to allow them to retire with dignity and purpose," Bush said. "We cannot do that with the fertility rates that we have in our country. We're below break-even today."
Part of the solution, he said, was encouraging more legal immigration that would add people to the workforce, thereby creating more payroll tax revenue.
"The one way that we can rebuild the demographic pyramid is to fix a broken immigration system to allow for people to come and learn English and play by our rules, to embrace our values and to pursue their dreams in our country with a vengeance to create more opportunities for all of us," said Bush, a longtime proponent for comprehensive immigration reform.
"This is a conservative idea," he continued. "If we do this we will rebuild our country in a way that will allow us to grow. If we don't do it we will be in decline, since productivity of this country is dependent upon young people who are equipped to work hard."
Bush, unlike many Republicans, has backed a pathway to legal status for undocumented immigrants, provided they pay fines and learn English. Such measures have been staunchly opposed by conservatives, who say allowing people who came to the United States illegally to remain here amounts to amnesty.
Bush's arguments for immigration reform were met with near silence from the conservative crowd Friday, and following his speech the former Florida governor received a polite standing ovation. Comparatively, Rep. Michele Bachmann, who used parts of her speech to decry the bill backed by a bipartisan group of eight senators as "amnesty" for undocumented immigrants, received loud applause.
Bush, who is speculated to be considering a run for the 2016 GOP presidential nomination, made his remarks the same week U.S. census data indicated rapid demographic changes, including showing for the first time that more non-Hispanic Whites died last year than were born.
The data also showed that Asians were the nation's fastest-growing demographic group, rising in population 2.9% last year. The Hispanic population grew by 2.2%, which the Census Bureau primarily attributed to a greater number of births than deaths.
In total, non-Hispanic Whites were the only racial group to have a negative rate of "natural increase" last year – meaning there were more deaths than births. Hispanics had 872,840 more births than deaths; African-Americans had 435,182; and Asians had 211,537.