When asking whether a border wall can pay for itself, the key questions are the cost of each illegal immigrant, and the number of illegal crossers, vs. the cost of a wall. Making reasonable estimates of these factors allows us to calculate what share of future illegal border-crossers the wall would have to stop or deter from trying to enter in order for the wall to be cost-effective. This updated analysis indicates that to pay for the president's $5 billion wall request, a wall would have to prevent about 60,000 crossings — or 3 to 4 percent of expected illegal crossers in the next decade. If we make much more conservative assumptions about both the cost of illegal immigrants and future flows, it still shows that a wall would have to stop or deter only a modest percentage of illegal crossings to pay for itself.
- In a prior analysis we took the likely education level of illegal border-crossers and applied fiscal estimates developed by the National Academies of Sciences, Engineering, and Medicine (NAS) for immigrants by education level — excluding their children. These estimates indicated an average lifetime net fiscal cost of $74,722 per illegal crosser — $82,191 in 2018 dollars.
- Analysis by the Institute for Defense Analyses (IDA) indicates that there are 1.95 to 2.28 apprehensions for every successful illegal crossing. This translates to about 170,000 to 200,000 successful illegal crossings in 2018, or 1.7 million to two million over the next 10 years, assuming this level continues.
- The House passed a funding bill before Christmas with $5 billion for the wall, which means the wall would have to stop or deter 3 to 4 percent (60,000) of the future illegal crossers over the next decade to pay for itself.
- If we make conservative alternative assumptions that illegal crossers cost half what we estimate, and we further assume the future flows will be only half the 2018 level, then the wall would have to stop or deter 12 to 14 percent of expected illegal border-crossers in the next decade.
Important Caveats About This Analysis
- In addition to crossing the border surreptitiously, aliens join the illegal population primarily by overstaying a temporary visa. A southern border wall would not address this part of the illegal flow.
- A large share of the net fiscal cost of illegal immigrants is at the state and local level, not the federal level. The costs of building the wall will be borne by the federal government.
- This analysis does not measure the effectiveness of a wall, but instead only demonstrates the share of future crossers a wall would need to stop in order to offset its cost.
- These cost estimates, based on the NAS research, only include original illegal immigrants, not their children and grandchildren. In our prior analysis, we found that if the cost of descendants is included, then the net fiscal drain raises to $94,391 — $103,826 in 2018 dollars.
- To create its long-term fiscal estimates for immigrants by education level, the NAS uses the concept of "net present value" (NPV). This concept, which is common in economics, has the effect of reducing the size of the net fiscal drain that less-educated immigrants, which describes most illegal immigrants, will create in the future. The NAS does this because costs or benefits years from now are valued less in economics relative to more immediate costs. If the actual net lifetime fiscal cost of illegal border-crossers were used it would likely roughly double the lifetime fiscal drain illegal crossers create. (We have a longer discussion of this issue in our original report. See the section "Do Net Present Values Make Sense?" The bottom line is that NPVs do make sense when thinking about the costs of a wall because the cost of a wall is immediate and with NPV the fiscal impact of illegal immigrants is also measured in current dollars.)
Cost per Illegal Immigrant
To estimate the fiscal cost of illegal immigrants in our prior analysis we applied the average net fiscal impact (taxes paid minus costs) of immigrants by education from a NAS study to the education level of illegal border-crossers. Based on that analysis, we estimate that each crosser creates a net cost of $74,722 (taxes paid minus costs) during his or her lifetime, excluding costs for their U.S.-born children. The figures from the NAS study are in 2012 dollars; converting them to 2018 dollars would raise them to $82,191. This estimate means that for every 100,000 illegal immigrants prevented from crossing illegally, it would save taxpayers $8.2 billion over the illegal immigrants' lifetimes.
As we discussed at length in our prior analysis, the primary factor driving these costs is the low education level of such a large share of illegal crossers. There is agreement among researchers that illegal immigrants overwhelmingly have modest levels of education — most have not completed high school or have only a high-school education. There is also agreement that immigrants who come to the United States with modest levels of education create significantly more in costs for government than they pay in taxes.
Number of Illegal Crossers
To determine the number of likely future border-crossers, we used research by the Institute for Defense Analyses (IDA) done under contract to the Department of Homeland Security. Their analysis indicates a ratio of one successful crossing for every 1.95 to 2.28 apprehensions on the Southern border.
For 2015, IDA estimated 170,000 people successfully crossed the southern border between ports of entry. For 2014, they estimate it was 210,000. (See table on p. iv). CBP reports 331,333 apprehensions on the Southwest border for 2015 and 479,371 for 2014 between ports of entry. (Crossings between ports of entry are what a wall is designed to prevent. Other forms of illegal entry are not relevant to a discussion of a wall.) This means that there is one successful illegal crosser for every 1.95 to 2.28 apprehensions, based on the 2014 and 2015 data. The years 2014 and 2015 are the most recent for which IDA has estimated the number of successful border-crossers. CBP data from 2018 show 396,579 apprehensions in 2018 between ports of entry. This implies that the number of successful crossers in 2018 was between 173,731 and 203,476, which we round to 170,000 and 200,000 in this report for convenience. (It should be noted that apprehension figures do not include those turned away at ports of entry for inadmissibility. These individuals are sometimes reported with apprehension figures.)
Illegal Crossings in the Future
The number of apprehensions fluctuates from year to year. The nearly 400,000 in 2018 was more than the 303,916 reported in 2017, but slightly less than the less than 408,870 in 2016. There is no way to know for certain what the level will be in the future; however, the lowest number in recent years was 2017, at more than 300,000. The scale of illegal migration along the southern border remains enormous. Illegal migration through the southern border is very likely to remain an attractive option for significant numbers of people throughout the world in the foreseeable future.
Cost of a Border Wall
The bill passed by the House of Representatives on December 20 contained $5 billion in wall funding. With this and the above numbers it is possible to determine if the wall can pay for itself. If the number of illegal crossing in 2018 was to continue for the next 10 years, the lifetime net fiscal drain from the 1.7 to two million new illegal immigrants would be $140 billion to $164 billion — $82,191 multiplied by the cost of each successful crosser. For a wall costing $5 billion to pay for itself, it would have to stop or deter 3 to 4 percent (about 60,000) of the expected successful illegal crossers over the next decade.
We can, of course, put different numbers into our model and see the results. If we assume that the number of successful illegal crossings in the next decade without a wall will be half (850,000 to one million) the 2018 level, and we further assume that the cost of each illegal crosser is half ($41,096) of what we have estimated, then the wall would have to stop or deter 12 to 14 percent of expected crossers in the next decade rather than the 3 to 4 percent. Alternatively, if the costs of illegal immigrants are higher than we have estimated and the level of future illegal crossings is also higher, then a wall would have to stop or deter a smaller share of than the 3 to 4 percent we report. But the range of reasonable assumptions indicates that a wall would not have to come close to being anywhere near 100 percent effective to pay for itself. This would be true even if a wall cost twice as much. A wall that is only partially effective could pay for itself by offsetting the cost that otherwise successful illegal crossers would create.