CROP PRODUCTION AND ROAD CONNECTIVITY IN SUB-SAHARAN AFRICA

**Table 4.1 The impact of road connectivity on crop production: Sub-Saharan Africa total**

|Equations|(1)|(2)|(3)|(4)|(5)|(6)|(7)|(8)|(9)|
|---|---|---|---|---|---|---|---|---|---|
|Dependent variable|Ln (tot|al crop produ<br>high-input)|ction,|Ln (tot<br>low-i|al crop produ<br>nput/subsiste|ction,<br>nce)|Ln (to|tal crop prod<br>irrigated)|uction,|
|Estimation method|IV-Tobit|IV-Tobit|IV-Tobit|IV-Tobit|IV-Tobit|IV-Tobit|IV-Tobit|IV-Tobit|IV-Tobit|
|Ln (travel time to nearest 25K cit)|–1.189***|||–2.251***|||–1.479***|||
|y|(0.075)|||(0.064)|||(0.089)|||
|Ln (travel time to nearest 100K cit)||–1.557***|||–2.864***|||–1.807***||
|y||(0.090)|||(0.079)|||(0.106)||
|L l i 500K i|||–1.593***|||–4.814***|||–3.508***|
|n (trave tme to nearest cty)|||(0.159)|||(0.153)|||(0.207)|
|Ln (otential roduction hih-inut)|1.193***|1.197***|1.194***|||||||
|p p gp|(0.010)|(0.010)|(0.010)|||||||
|L ttil dti lit||||0.257***|0.247***|0.283***||||
|n (poena proucon ow-npu)||||(0.008)|(0.008)|(0.008)||||
|Ln (otential roduction irriated)|||||||0.410***|0.417***|0.402***|
|p p g|||||||(0.008)|(0.008)|(0.009)|
|Ln (oulation)|0.115***|0.119***|0.132***|0.159***|0.163***|0.192***|0.020**|0.031***|0.045***|
|pp|(0.007)|(0.007)|(0.006)|(0.005)|(0.006)|(0.006)|(0.008)|(0.008)|(0.008)|
|L ihb lti t|0.249***|0.104***|0.180***|–0.093***|–0.328***|–0.728***|–0.308***|–0.453***|–0.855***|
|n (negor popuaon aggregae)|(0.029)|(0.035)|(0.050)|(0.025)|(0.030)|(0.046)|(0.035)|(0.042)|(0.064)|
|Country dummies|yes|yes|yes|yes|yes|yes|yes|yes|yes|
|Constant|yes|yes|yes|yes|yes|yes|yes|yes|yes|
|Wald test of exogeneity|235.50|252.75|87.31|1,146.17|1,286.72|1,188.36|343.29|378.44|469.19|
|(p-value)|0.000|0.000|0.000|0.000|0.000|0.000|0.000|0.000|0.000|
|Left-censored observations|25,793|25,793|25,793|10,990|10,990|10,990|34,780|34,780|34,780|
|Uncensored observations|100,189|100,189|100,189|116,677|116,677|116,677|71,742|71,742|71,742|
|Total observations|125,982|125,982|125,982|127,667|127,667|127,667|106,522|106,522|106,522|

_Source:_ Own calculations. _Note:_ 1. Ln (x) refers to the natural logarithm of variable x.

2. Total crop production (value) is the 20-crop aggregate using the medians of African country-level crop prices.

3. Standard errors in parentheses.

4. * significant at 10 percent; ** significant at 5 percent; *** significant at 1 percent.

The second broad pattern observable in these regressions is that the elasticities of travel time on crop production under the low-input crop-production system are almost two times higher than those under high-input and irrigated systems. For example, a 1 percent reduction in travel time to the nearest city with 100,000 people or more increases low-input crop production by 2.9 percent, but results in only a 1.6 percent increase in high-input crop production and a 1.8 percent increase in irrigated crop production. For travel time to the nearest city with 500,000 people or more, the elasticity on low-input production is –4.8, compared to –1.6 for high-input and –3.5 for irrigated production. For travel time to the nearest city with 25,000 people or more, the same coefficients are –2.3, –1.2, and –1.5, respectively. As discussed below, the implied own-price elasticities of supply from these regressions are extremely high, suggesting that these travel-time elasticities are capturing a long-term relationship involving the location of population 15