Stakeholders in agricultural development in Nigeria are currently confronted with the onerous task of feeding over hundred million people in the nation. The paper attempts to examine the trends in the production, area and productivity of cocoyam in Nigeria from 1960/61 to 2003/06 in two periods and highlights the relative contributions of area and productivity to the observed growth. Results reveal that output, area and productivity of cocoyam exhibited negative trends in Period I, (Pre-SAP, 1960/61-1984/85) whereas output and area of cocoyam showed positive trend in Period II (Post-SAP, 1985/86-2003/06). Increases in cocoyam production were due principally to the expansion of area under cultivation. Measures aimed at improving the yield and efficiency of resource utilization will enhance the prospect of cocoyam.Econometric Trend, Cocoyam

Asumugha, G.N

Okezie, C.A

Okoye, B.C

Onyenweaku, C.E

Tanko, L

English

Research Papers in Economics

ECONOMETRIC ASSESSMENT OF THE TREND IN COCOYAM 
PRODUCTION IN NIGERIA, 1960/61-2003/2006. 
 
Okoye, B.C
1; Asumugha, G.N
1; Okezie, C.A
2; Tanko,L
3 and Onyenweaku, C.E
2 
1 National Root Crops Research Institute (NRCRI) Umudike, P.M.B 7006,   
   Umuahia. 
2. Department of Agricultural Economics, Michael Okpara University of  
    Agriculture, Umudike. P.M.B 7267, Umuahia, Abia State. 
3.Department of Agricultural Economics and Extension, Federal University of     
   Technology Minna, Niger State 
 
ABSTRACT 
Stakeholders in agricultural development in Nigeria are currently confronted with the 
onerous task of feeding over hundred million people in the nation. The paper attempts to 
examine the trends in the production, area and productivity of cocoyam in Nigeria from 
1960/61 to 2003/06 in two periods and highlights the relative contributions of area and 
productivity to the observed growth. Results reveal that output, area and productivity of 
cocoyam  exhibited  negative  trends  in  Period  I,  (Pre-SAP,  1960/61-1984/85)  whereas 
output  and  area  of  cocoyam  showed  positive  trend  in  Period  II  (Post-SAP,  1985/86-
2003/06). Increases in cocoyam production were due principally to the expansion of area 
under  cultivation.  Measures  aimed  at  improving  the  yield  and  efficiency  of  resource 
utilization will enhance the prospect of cocoyam. 
 
INTRODUCTION 
Countries  in  the  African  continent  face  an  ever-increasing  food  crisis  as  the 
effective demand for food in these countries continue to outpace demand. It is estimated 
that Nigeria has a land area of about 98.3million hectares out of which about 71.2million 
hectares or 70 percent are cultivable while only about 34million hectares or roughly one 
third of the country’s total land area is under cultivation (FMED, 1975). Self-sufficiency 
in food has remained elusive in spite of the high potential for increasing food production 
in the country by expanding the area under cultivation and improving productivity from 
existing  cropped  area.  Over  the  years,  Nigeria  has  had  to  resort  to  massive  food 
importation evidenced by the rising food import bill. This is because, the level of food 
production no longer keeps pace with demand. 
Cocoyam ranks third in importance after cassava and yam among the root and 
tuber crops cultivated and consumed in Nigeria. Available statistics show that Nigeria is 
the world’s leading producer of cocoyam (taro) which accounted for 3.5million metric 
tonnes  during  the  2003  cropping  season  (FAO,2006).  Despite  this,  the  objective  of 
sustainability in food production has remained a mirage as its cultivation has been shown 
to be declining (Onyenweaku and Ezeh, 1987; Zuhair and Hunter, 2003). 
Given  that  cocoyam  is  an  important  staple  food  in  Nigeria,  any  attempt  to 
improve its productivity would be a right step towards the resolution of the food crisis. 
This  study  is  further  justified  by  the  need  to  having  a  better  understanding  of  the 
performance of the crop sub-sector as this is an issue of concern to both government and 
individual planners. To this end therefore, this study attempts to examine the trends in the 
production,  area  cultivated  and  productivity  of  cocoyam  in  Nigeria  from  1960/61  to   2 
2003/2006  and  highlights  the  relative  contributions  of  area  and  productivity  to  the 
observed growth. 
 
METHODOLOGY 
a)  The Data: 
  Secondary data sourced from various issues of Central Bank of Nigeria 
(CBN) Statistical Bulletin and Federal Office of Statistics (FOS) on area, output and 
productivity  (yield)  of  cocoyam  in  Nigeria  from  1960-2006  were  used  for  the 
analysis. 
b)  The Model and Analysis of Data: 
        The growth rates were computed by fitting exponential function in time to the 
data following Onyenweaku and Ezeh (1987). The lead equation was chosen for further 
analysis based on the normal economic, econometric and statistical criteria. The fitted 
function is specified as follows: 
  Exponential:         Y =b0 e
bt          ………………..… (1) 
  When linearized in logarithms, equation (1) becomes: 
  InY = b0 + b1t             ………………..… (2) 
                    Y= production, area or productivity 
                    t = time trend variable 
                    b0, b1, = regression parameters to be estimated 
  The growth rate (r) is given by 
                   r = b x100/1                     ………… … (3) 
Where: 
  This measure has proven to be more realistic in computing growth rates as it takes 
into  account  the  entire  observations.  Alternative  methods  of  computing  compound 
growth rates exist. One of these is to use data at the beginning and at the end of a period 
which has been shown to ignore vital information. 
           Data  were  fitted  to  the  above  function  in  estimating  production,  area  and 
productivity  for  two  periods,  namely:  Pre-SAP  (Structural  Adjustment  Programme)-
(1960/61-1984/85) called Period I and Post-SAP (1985/86-2003/06) Period II. 
 
RESULTS AND DISCUSSION 
  a) Growth of Production, Area and Productivity. 
Results of the estimated log linear function in time variable for cocoyam output, area and 
productivity for the two periods which is used for further analysis are presented in Table 
1. Output, Area and Productivity of cocoyam exhibited negative trends in Period I. In this 
Period, the coefficient of the trend variable is significantly different from zero at 1% for 
output,  area  and  productivity  of  cocoyam.  In  Period  II  however,  output  and  area  of 
cocoyam showed positive trends. The productivity coefficient also depicted a positive 
trend in Period II. The coefficient of the time trend is highly significant at 1% for area 
and production except productivity whereby the coefficient is significant at 5%. This is 
an indication that the Structural Adjustment Programme (SAP) stimulated investment in 
especially cocoyam production in Nigeria. The study thus validates empirically that the 
Structural Adjustment Programme (SAP) which ushered in the era of deregulation is an 
important step in stimulating and sustaining food production in Nigeria. Overall, the data 
shows a positive trend relationship between time and cocoyam production in Nigeria.   3 
Attainment of aggregate growth in the production of cocoyam in Nigeria is feasible under 
exchange rate deregulation. The administrative fixation which was the practice before 
1986 was not a good policy. The attainment of food security in Nigeria requires that 
government policies on those factors which best explain staple food crop production such 
as technology, agricultural input subsidy and exchange rate etc. 
 
(b)  Growth  Rates  of  Production,  Area  and  Productivity  of  Cocoyam  in  Nigeria, 
1960/61-2003/06 (%) 
  Compound growth rates of production, area and productivity of cocoyam for the 
two Periods were computed and presented in Table 2. The growth rates of production, 
area and productivity of cocoyam were all found to be significantly different statistically 
for the two periods. The output of cocoyam declined in the first period by 10.80 percent 
per annum but increased by 14.30 percent per annum in period II, suggesting that SAP 
positively influenced the production of cocoyam by increasing the level of investments. 
A similar trend was observed in the growth rates of area allocated to cocoyam. In Period 
I, the area under cocoyam declined by 6.90 percent per annum but increased by 12.60 
percent  per  annum  in  Period  II.  The  growth  rates  of  productivity  of  cocoyam  also 
declined in the Pre-SAP era (Period I) by 0.80 percent. The productivity of cocoyam 
however increased to a compound rate of 1.70 percent per annum during the Post-SAP 
era.  The  era  of  negative  growth  rates  in  cocoyam  output  and  area  appears  to  have 
commenced in 1960/61 that is the beginning of the first period. The findings suggest that 
increases in cocoyam output in Nigeria between Periods I and II were due mainly to 
expansion of area under cultivation and not the productivity/yield (output/hectare). 
 
CONCLUSION  
           The  estimated  functions  suggested  positive  trends  in  the  production,  area  and 
productivity of cocoyam between periods I (1960/61-1984/85) and II (1985/86-2003/06). 
Increases in cocoyam production were due principally to the expansion of area under 
cultivation and increased investment. The findings show that growth in staple food crop 
production  in  Nigeria  especially  cocoyam  is  possible  especially  in  the  era  of  guided 
deregulation. Appropriate policy on agricultural input supply, research and extension will 
provide the required sector-specific incentive for enhanced productivity. Measures aimed 
at improving the yield and efficiency of resource utilization will enhance the prospects of 
cocoyam. 
 
REFERENCES 
Food and Agricultural Organisation (FAO) (2006). “Food Crop and Storage”, 
Corporate Document REPOSITORY and Databases.  
Federal Ministry of Economic Development (FMED) (1975). The Third National 
Development Plan, 1975-1980, Lagos. 
Onyenweaku, C.E. and N.O.A.Ezeh (1987). “Trend in Production, Area and 
Productivity in cocoyam in Nigeria 1960/61-1981/84”, Paper Presented at the Conference 
organized by the National Root Crop Research Institute, Umudike. 
Onyenweaku, C.E. and Okoye B.C (2005). “Trends in Cassava Output, Area and 
Productivity in Nigeria, 1960/61-2003/04”, Paper presented at the Proceedings of the 39
th  
Conference of the Agricultural Society of Nigeria, Benin 2005.   4 
Zuhair, M. and D.G. Hunter (2000). Taro cultivation and use in the Maldives. 
IPGRI session. 12
th  symposium of ISTRC; Tsukuba Japan: 97. 
 
Table 1. Estimated Functions for Production, Area and Productivity of Cocoyam in  
               Nigeria, 1960/61-2003/04. 
Note:   Figures in parentheses are the respective t-ratios; ***, ** and * implies   
              significance at 1%, 5% and 10% levels respectively. 
 
 
Table 2. Computed Growth rates of Production, Area and      
  Productivity of Cocoyam in Nigeria, 1960/61-2003/04 (%). 
          Period         Production         Area         Productivity 
 
1. Period I  
   (1960/61-1984/85)  -10.236**    -6.667**  -5.256** 
2. Period II  
   (1985/86-2003/04)   21.650**    13.427**  6.929** 
 
    ** Significant at 5 percent 
            
 
I)  PRODUCTION    Estimated 
Coefficient(s) 
   
  Constant (b0)    b1     R
2  F value 
  a) Period I (1960/61-
1984/85) 
7.864 
(47.500)*** 
-0.108 
(-9.720)*** 
0.80  94.556*** 
  b) Period II 
(1985/86-2003/04) 
5.838 
(49.234)*** 
0.143 
(13.798)*** 
0.92  190.072*** 
II)  AREA         
  a) Period I (1960/61-
1984/85) 
6.028 
(26.891)*** 
-0.069 
(-4.557)*** 
0.47  20.681*** 
  b) Period II (1985/86-
2003/04) 
4.333 
(54.038)*** 
0.126 
(17.983)*** 
0.95  323.290*** 
  4.326 
(32.560)*** 
0.129 
(4.207)*** 
0.95  152.180*** 
 
III)  PRODUCTIVITY 
       
  a) Period I (1960/61-
1984/85) 
1.558 
(15.882)*** 
-0.008 
(-1.56) 
0.10  2.431 
  b) Period II (1985/86-
2003/04) 
1.505 
(24.057)*** 
0.017 
(3.058)** 
0.35  9.293**   5 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Agricultural Organisation (FAO)

Federal Ministry of Economic Development (FMED)

Trends in Cassava Output, Area and Productivity in Nigeria, 1960/61-2003/04”, Paper presented at the

Econometric Assessment of the Trend in Cocoyam Production in Nigeria, 1960/61-2003/2006

Econometric Assessment of the Trend in Cocoyam Production in Nigeria, 1960/61-2003/2006

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