A 2008 meta-analysis, which examined 62 empirical research studies between 1996 and 2006, relating to domestic violence in heterosexual intimate relationships from adolescence through to adulthood in the United States, reported on research findings that consistently show that adolescent females commit significantly more acts of domestic violence in intimate relationships than adolescent males. It stated, however, that the "data also suggest that females who commit acts of domestic violence may experience more violent or frequent IPV victimization than males" and that "highest rates [for female-perpetrated IPV were found for emotional violence, followed by physical and sexual violence. Prevalence rates varied widely within each population, most likely due to methodological and sampling differences across studies." The authors added, "Few longitudinal studies existed, limiting the extent to which we could identify developmental patterns associated with female perpetrated intimate partner violence." They found a few studies which reported prevalence rates of IPV perpetration among females at two or more time points, which they stated made "it difficult to obtain a clear picture of the developmental patterns associated with this type of violence." There was also only one study that reported on prevalence rates over time for female perpetrated IPV among adolescents. "This study found a significant increase in prevalence over a six month period; however, they measured lifetime perpetration of IPV, therefore, it is unclear if there was an actual increase or simply an accumulation of violence," stated the authors. "Together, these studies provide very limited evidence that female perpetration of IPV may follow a similar developmental trajectory as other forms of violence. [...] Unfortunately, many of the studies included in this review used modified or alternative instruments making it difficult to accurately compare prevalence estimates."