A "parametric" or "top down" estimate uses validated relationships among cost, schedule, and measurable attributes of systems, hardware, and software.
In most cases, he has found that the top-down estimates are appreciably higher.
More reductions in top-down estimates of overall growth by Wall Street economists are expected this week, only heightening the likelihood that earnings projections will eventually have to come down, too.
If you look at the top-down estimates for the S&P 500, they're running….
Figure 2 shows an aggregated bottom-up economic risk estimate in comparison with top-down estimates available in existing studies.
Our estimate of global livestock CH4 C emissions is similar to top-down estimates made using atmospheric inversion methods [20] (Table 5).
Our estimates for the US, however, are smaller than recent top-down estimates by 21 51% [20], 46%[23]], or 30%[21]].
Likewise, the revised manure management CH4 emissions for year 2011 in the US were 71.8% higher than IPCC-based estimates, consistent with recently reported top-down estimates.
Recent top-down estimates for the US, however, suggest that even revised methods based on IPCC guidelines underestimate livestock CH4 emissions in recent years at the national or state level [20 23].
These results show that our emissions estimates, if modified to reflect local conditions, are similar to or smaller than recent top-down estimates in California, where livestock and fossil fuel-sector CH4 emissions are spatially well separated.
