Table 2.

Demographic characteristics of the ZIP-codes in which the trials open by presence of English fluency requirements. Trials with missing ZIP-code data and those opened before 1995 were excluded. SD=standard deviation, IQR=inter-quartile range. The statistics summarize the percents among ZIP-codes. For example, the means depict the average of the percent characteristics among ZIP-codes. Of those trials with at least one ZIP-code level characteristic missing, 193 (7.3%) of 2,650 trials required English fluency.

ZIP-code Level Characteristics	No English Language Restrictions	Requires English Fluency	P-value
Percent responding that they speak English only	n=7,225	n=559
Mean (SD)	76.2% (14.0%)	76.4% (13.0%)	p=0.83
Median (IQR)	78.4% (70.4%–85.8%)	78.1% (69.9%–86.2%)
Percent responding that they speak English less than “very well”	n=7,225	n=559
Mean (SD)	17.3% (9.5%)	17.7% (9.5%)	p=0.24
Median (IQR)	16.1% (10.3%–22.2%)	17.5% (10.0%–24.0%)
Percent with incomes below the poverty level	n=7,117	n=544
Mean (SD)	21.9% (15.2%)	23.2% (15.6%)	0.045
Median, IQR	18.1% (11.6% – 29.0%)	19.7% (10.7%–31.1%)
Percent responding that they are White alone	n=7,269	n=564
Mean (SD)	57.0% (20.4%)	56.3% (20.9%)	p=0.49
Median (IQR)	59.6% (45.5%–71.0%)	58.4% (42.1%–73.1%)
Percent responding that they are Black/African American alone	n=7,269	n=564
Mean (SD)	17.1% (17.5%)	17.7% (19.5%)	p=0.43
Median (IQR)	11.6% (5.1%–22.2%)	10.0% (4.2%–22.8%)
Percent responding that they are Asian alone	n=7,269	n=564
Mean (SD)	9.6% (9.2%)	11.1% (11.0%)	0.0002
Median (IQR)	7.0% (3.9%–12.4%)	8.4% (3.8%–14.7%)
Percent responding that they are Hispanic alone	n=7,269	n=564
Mean (SD)	13.4% (14.4%)	11.9% (12.5%)	0.012
Median (IQR)	9.1% (4.6%–15.7%)	7.9% (4.2%–14.0%)