The soaring number of migrant arrivals along the U.S. southern border over the past year and a half has fueled dire humanitarian challenges, strained government resources and created a political liability for President Biden.

In some ways, the migration flows across the U.S.-Mexico border during the Biden administration are unprecedented. Arrests of individuals who crossed the U.S. southern border illegally have reached all-time highs. Arrivals of migrants from certain countries, including Cuba and Venezuela, have set new records.  But by other measurements, including overall illegal entries, the latest migration wave is not unprecedented. 

Despite the recent record levels of migrant arrests, there were more unlawful entries in the mid and early 2000s, when the U.S had fewer resources and personnel to apprehend border-crossers, according to government data obtained by CBS News. An unusually high rate of repeat crossings during the coronavirus pandemic has also inflated the border arrest tallies.

Here are the facts about arrivals of migrants along the U.S.-Mexico border during the Biden administration.

Border arrests have reached record levels

Border Patrol, an agency within Customs and Border Protection (CBP), apprehends migrants who enter the U.S. illegally in between ports of entry. The Office of Field Operations, another CBP agency, facilitates commercial, pedestrian and other forms of lawful traffic, while processing migrants who seek asylum at ports of entry, which is legal under U.S. law.

In fiscal year 2021, which included Mr. Biden's first eight full months in office, Border Patrol recorded 1.66 million arrests along the southern border, surpassing the previous all-time high of 1.64 million arrests set in 2000, CBP data show.During the first 10 months of fiscal year 2022, Border Patrol agents along the Mexican border reported more than 1.8 million apprehensions, a new record high that will likely surpass 2 million when fiscal year 2023 starts in October, according to the CBP figures.These figures do not include migrants processed at ports of entry along the southern border, where the Biden administration has processed some migrant groups, including Ukrainian refugees, those returned to Mexico under discontinued Trump-era rules and asylum-seekers determined to be vulnerable.In fiscal year 2021, 75,000 migrants were processed by the Office of Field Operations at ports of entry along the Mexican border. That number has climbed to 130,000 during the first 10 months of fiscal year 2022

An unprecedented demographic shift 

Before the early 2010s, the vast majority of border-crossers taken into U.S. custody were from Mexico, typically men without children traveling in search of work.That trend shifted in subsequent years when migrants from Guatemala, Honduras and El Salvador started journeying north in greater numbers.