percentage increases in interior floor area and interior volume it is estimated that in comparison with other prior art bathtubs with increased sloping and bottom rounded sides the savings can be up to approximately 35 increase in interior floor area and interior air volume bathtub 15 of this invention also offers safety improvement over that of the prior art safety studies indicate over 234 000 bathroom injuries each year of which 81 percent occurred because of falls in the bathroom of these injuries more than one third happen while bathing or showing the center for disease controls cdc estimates that 9 8 percent of all bathroom injuries specifically occur when getting out of a bathtub which equals at least 22 932 injuries fig8 shows a profile of a person 42 exiting a prior art bathtub 40 with rounded walls at the bottom the u201c average person u201d 42 is a composite 50 th percentile man or woman with a hip joint to floor dimension l of 35 inches although the results of the analysis to follow are somewhat dependent on this selected number let it be said that a taller person would experience slightly less difference in egress from either a prior art tub or the tub 15 of fig3 9 of this invention and vice versa for a shorter person.