In addition to these data limitations, a substantial fraction of "research" on immigration has a tendentious quality that belies its nominally objective basis. The findings of immigration research also appear to be acutely sensitive to certain critical assumptions. In one recent and disturbing case, two groups of analysts assessed the difficult and contentious question of whether immigrants pay more or less taxes than they receive in social benefits. The research teams used similar datasets and cost-benefit analytic frameworks, yet embraced sharply differing accounting assumptions about revenues and services to include. The result: one study concluded that there was an annual net cost of $40 billion, while the other that there was an annual net benefit of $27 billion.