Using Social Security (SocS) records covering the universe of Spanish employees and firms, we compare firms' employment dynamics between 2013-2024 to those obtained from the Bank of Spain's microdata drawn from firms' balance sheets (CBI) as well as those of U.S. firms. Compared with CBI, SocS reveals less volatile aggregate employment growth and higher job reallocation rates driven by firms' large employment adjustments. Worker reallocation in Spain remains below U.S. levels and did not decline after the 2022 labor reform. SocS also highlights the central role of small firms in Spanish job creation and documents a left-shifted firm-size distribution relative to the U.S. Start-ups entering smaller, having lower survival probabilities, and weaker employment growth among survivors all contribute to a smaller Spanish firm size.