"In the sixteen-year (2004–2019) combined samples of young adults aged 21–30, 1.5% report having ever used any drug by injection not under a doctor’s orders, and 0.5% reported doing so on 40 or more occasions (Table 4-1a). Thus, about 1 in every 67 respondents has ever used an illicit drug by injection, and about 1 in every 200 respondents reports an extended pattern of use as indicated by use on 40 or more occasions. There are appreciable gender differences—2.2% of males vs. 0.9% of females indicate ever injecting a drug (p<.001), and the percentages saying they injected on 40 or more occasions are 0.7% for males and 0.3% for females (p<.001). The percentages of young adults who have injected drugs during the past 12 months without medical supervision are considerably smaller: 0.5% overall—1 in every 200 respondents—including 0.8% of males and 0.3% of females (p<.001). The percentages using 40 or more times in the past 12 months are 0.2% overall—0.3% for males and 0.1% for females."
Johnston, L. D., O’Malley, P. M., Bachman, J. G., Schulenberg, J. E., Patrick, M. E., & Miech, R. A. (2020). HIV/AIDS: Risk & Protective Behaviors among Adults Ages 21 to 30 in the U.S., 2004–2019. Ann Arbor: Institute for Social Research, The University of Michigan.